31997521 has 2 divisors, whose sum is σ = 31997522. Its totient is φ = 31997520.

The previous prime is 31997513. The next prime is 31997533. The reversal of 31997521 is 12579913.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31979025 + 18496 = 5655^2 + 136^2 .

It is a cyclic number.

It is not a de Polignac number, because 31997521 - 2³ = 31997513 is a prime.

It is equal to p_1973656 and since 31997521 and 1973656 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (31997551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15998760 + 15998761.

It is an arithmetic number, because the mean of its divisors is an integer number (15998761).

Almost surely, 2^31997521 is an apocalyptic number.

It is an amenable number.

31997521 is a deficient number, since it is larger than the sum of its proper divisors (1).

31997521 is an equidigital number, since it uses as much as digits as its factorization.

31997521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17010, while the sum is 37.

The square root of 31997521 is about 5656.6351305348. The cubic root of 31997521 is about 317.4720119169.

The spelling of 31997521 in words is "thirty-one million, nine hundred ninety-seven thousand, five hundred twenty-one".