21087275 has 18 divisors (see below), whose sum is σ = 28745556. Its totient is φ = 15334000.

The previous prime is 21087221. The next prime is 21087277. The reversal of 21087275 is 57278012.

It is not a de Polignac number, because 21087275 - 2⁶ = 21087211 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21087277) 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, 461 + ... + 6510.

Almost surely, 2^21087275 is an apocalyptic number.

21087275 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21087275 is a deficient number, since it is larger than the sum of its proper divisors (7658281).

21087275 is a wasteful number, since it uses less digits than its factorization.

21087275 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7003 (or 6987 counting only the distinct ones).

The product of its (nonzero) digits is 7840, while the sum is 32.

The square root of 21087275 is about 4592.0883049001. The cubic root of 21087275 is about 276.2740879742.

The spelling of 21087275 in words is "twenty-one million, eighty-seven thousand, two hundred seventy-five".