21687475 has 18 divisors (see below), whose sum is σ = 27433140. Its totient is φ = 17007120.

The previous prime is 21687473. The next prime is 21687499. The reversal of 21687475 is 57478612.

It is not a de Polignac number, because 21687475 - 2¹ = 21687473 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21687473) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 155956 + ... + 156094.

Almost surely, 2^21687475 is an apocalyptic number.

21687475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21687475 is a deficient number, since it is larger than the sum of its proper divisors (5745665).

21687475 is an equidigital number, since it uses as much as digits as its factorization.

21687475 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 307 (or 223 counting only the distinct ones).

The product of its digits is 94080, while the sum is 40.

The square root of 21687475 is about 4656.9813184079. The cubic root of 21687475 is about 278.8707708625.

The spelling of 21687475 in words is "twenty-one million, six hundred eighty-seven thousand, four hundred seventy-five".