15861987 has 20 divisors (see below), whose sum is σ = 24463296. Its totient is φ = 10231920.

The previous prime is 15861971. The next prime is 15861991. The reversal of 15861987 is 78916851.

It is not a de Polignac number, because 15861987 - 2⁴ = 15861971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (15861907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 648 + ... + 5669.

Almost surely, 2^15861987 is an apocalyptic number.

15861987 is a deficient number, since it is larger than the sum of its proper divisors (8601309).

15861987 is an equidigital number, since it uses as much as digits as its factorization.

15861987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6360 (or 6351 counting only the distinct ones).

The product of its digits is 120960, while the sum is 45.

The square root of 15861987 is about 3982.7110113590. The cubic root of 15861987 is about 251.2575938894.

The spelling of 15861987 in words is "fifteen million, eight hundred sixty-one thousand, nine hundred eighty-seven".