15697921 has 4 divisors (see below), whose sum is σ = 15850432. Its totient is φ = 15545412.

The previous prime is 15697907. The next prime is 15697943. The reversal of 15697921 is 12979651.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-15697921 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15697901) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76101 + ... + 76306.

It is an arithmetic number, because the mean of its divisors is an integer number (3962608).

Almost surely, 2^15697921 is an apocalyptic number.

It is an amenable number.

15697921 is a deficient number, since it is larger than the sum of its proper divisors (152511).

15697921 is a wasteful number, since it uses less digits than its factorization.

15697921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152510.

The product of its digits is 34020, while the sum is 40.

The square root of 15697921 is about 3962.0601964130. The cubic root of 15697921 is about 250.3883085536.

The spelling of 15697921 in words is "fifteen million, six hundred ninety-seven thousand, nine hundred twenty-one".