15916597921 has 27 divisors (see below), whose sum is σ = 18865829619. Its totient is φ = 13389214608.

The previous prime is 15916597919. The next prime is 15916597927. The reversal of 15916597921 is 12979561951.

The square root of 15916597921 is 126161.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 1047234321 + 14869363600 = 32361^2 + 121940^2 .

It is not a de Polignac number, because 15916597921 - 2¹ = 15916597919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (15916597927) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 59169375 + ... + 59169643.

Almost surely, 2^15916597921 is an apocalyptic number.

15916597921 is the 126161-st square number.

15916597921 is the 63081-st centered octagonal number.

It is an amenable number.

15916597921 is a deficient number, since it is larger than the sum of its proper divisors (2949231698).

15916597921 is an frugal number, since it uses more digits than its factorization.

15916597921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 686 (or 343 counting only the distinct ones).

The product of its digits is 1530900, while the sum is 55.

The spelling of 15916597921 in words is "fifteen billion, nine hundred sixteen million, five hundred ninety-seven thousand, nine hundred twenty-one".