15987921 has 8 divisors (see below), whose sum is σ = 22244160. Its totient is φ = 10195152.

The previous prime is 15987913. The next prime is 15987931. The reversal of 15987921 is 12978951.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 15987921 - 2³ = 15987913 is a prime.

It is a super-2 number, since 2×15987921² = 511227235804482, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (15987901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 115786 + ... + 115923.

It is an arithmetic number, because the mean of its divisors is an integer number (2780520).

Almost surely, 2^15987921 is an apocalyptic number.

It is an amenable number.

15987921 is a deficient number, since it is larger than the sum of its proper divisors (6256239).

15987921 is a wasteful number, since it uses less digits than its factorization.

15987921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 231735.

The product of its digits is 45360, while the sum is 42.

The square root of 15987921 is about 3998.4898399271. The cubic root of 15987921 is about 251.9207832387.

The spelling of 15987921 in words is "fifteen million, nine hundred eighty-seven thousand, nine hundred twenty-one".