21987575 has 12 divisors (see below), whose sum is σ = 27330840. Its totient is φ = 17547360.

The previous prime is 21987571. The next prime is 21987601. The reversal of 21987575 is 57578912.

It is not a de Polignac number, because 21987575 - 2² = 21987571 is a prime.

It is a hoax number, since the sum of its digits (44) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21987571) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 13136 + ... + 14714.

It is an arithmetic number, because the mean of its divisors is an integer number (2277570).

Almost surely, 2^21987575 is an apocalyptic number.

21987575 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21987575 is a deficient number, since it is larger than the sum of its proper divisors (5343265).

21987575 is a wasteful number, since it uses less digits than its factorization.

21987575 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2146 (or 2141 counting only the distinct ones).

The product of its digits is 176400, while the sum is 44.

The square root of 21987575 is about 4689.0910633085. The cubic root of 21987575 is about 280.1511726186.

The spelling of 21987575 in words is "twenty-one million, nine hundred eighty-seven thousand, five hundred seventy-five".