21987567 has 24 divisors (see below), whose sum is σ = 36427040. Its totient is φ = 12519360.

The previous prime is 21987557. The next prime is 21987571. The reversal of 21987567 is 76578912.

21987567 is a `hidden beast` number, since 2 + 1 + 9 + 87 + 567 = 666.

It is not a de Polignac number, because 21987567 - 2¹⁰ = 21986543 is a prime.

It is a Duffinian number.

Its product of digits (211680) is a multiple of the sum of its prime divisors (1260).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987547) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 26109 + ... + 26937.

Almost surely, 2^21987567 is an apocalyptic number.

21987567 is a deficient number, since it is larger than the sum of its proper divisors (14439473).

21987567 is a wasteful number, since it uses less digits than its factorization.

21987567 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1263 (or 1260 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The square root of 21987567 is about 4689.0902102647. The cubic root of 21987567 is about 280.1511386417.

The spelling of 21987567 in words is "twenty-one million, nine hundred eighty-seven thousand, five hundred sixty-seven".