21087475 has 12 divisors (see below), whose sum is σ = 26214840. Its totient is φ = 16827200.

The previous prime is 21087457. The next prime is 21087491. The reversal of 21087475 is 57478012.

It is a happy number.

It is not a de Polignac number, because 21087475 - 2⁹ = 21086963 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21087475.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12216 + ... + 13834.

It is an arithmetic number, because the mean of its divisors is an integer number (2184570).

Almost surely, 2^21087475 is an apocalyptic number.

21087475 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21087475 is a deficient number, since it is larger than the sum of its proper divisors (5127365).

21087475 is a wasteful number, since it uses less digits than its factorization.

21087475 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2150 (or 2145 counting only the distinct ones).

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 21087475 is about 4592.1100814332. The cubic root of 21087475 is about 276.2749614021.

The spelling of 21087475 in words is "twenty-one million, eighty-seven thousand, four hundred seventy-five".