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397 is a prime number

397 has 2 divisors, whose sum is σ = 398. Its totient is φ = 396.

The previous prime is 389. The next prime is 401. The reversal of 397 is 793.

Subtracting from 397 its sum of digits (19), we obtain a triangular number (378 = T27).

Multipling 397 by its reverse (793), we get a triangular number (314821 = T793).

It can be divided in two parts, 3 and 97, that added together give a square (100 = 102).

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 361 + 36 = 19^2 + 6^2 .

397 is a truncatable prime.

It is a cyclic number.

It is not a de Polignac number, because 397 - 23 = 389 is a prime.

It is a plaindrome in base 13 and base 16.

It is a nialpdrome in base 11.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (307) by changing a digit.


It is a polite number, since it can be written as a sum of consecutive naturals, namely, 198 + 199.

It is an arithmetic number, because the mean of its divisors is an integer number (199).

397 is the 12-th hex number.

It is an amenable number.


397 is an equidigital number, since it uses as much as digits as its factorization.

397 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 189, while the sum is 19.

The square root of 397 is about 19.9248588452. The cubic root of 397 is about 7.3495965966.

The spelling of 397 in words is "three hundred ninety-seven", and thus it is an aban number and an oban number.