15981921 has 16 divisors (see below), whose sum is σ = 25070400. Its totient is φ = 10027584.

The previous prime is 15981893. The next prime is 15981947. The reversal of 15981921 is 12918951.

It is not a de Polignac number, because 15981921 - 2¹⁰ = 15980897 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (15981971) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 16951 + ... + 17868.

It is an arithmetic number, because the mean of its divisors is an integer number (1566900).

Almost surely, 2^15981921 is an apocalyptic number.

It is an amenable number.

15981921 is a deficient number, since it is larger than the sum of its proper divisors (9088479).

15981921 is a wasteful number, since it uses less digits than its factorization.

15981921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34845 (or 34839 counting only the distinct ones).

The product of its digits is 6480, while the sum is 36.

The square root of 15981921 is about 3997.7394862597. The cubic root of 15981921 is about 251.8892654068.

The spelling of 15981921 in words is "fifteen million, nine hundred eighty-one thousand, nine hundred twenty-one".