21521875 has 24 divisors (see below), whose sum is σ = 27560736. Its totient is φ = 16800000.

The previous prime is 21521849. The next prime is 21521893. The reversal of 21521875 is 57812512.

It is not a de Polignac number, because 21521875 - 2²¹ = 19424723 is a prime.

It is a super-2 number, since 2×21521875² = 926382207031250, which contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 221827 + ... + 221923.

It is an arithmetic number, because the mean of its divisors is an integer number (1148364).

Almost surely, 2^21521875 is an apocalyptic number.

21521875 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21521875 is a deficient number, since it is larger than the sum of its proper divisors (6038861).

21521875 is an frugal number, since it uses more digits than its factorization.

21521875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 173 counting only the distinct ones).

The product of its digits is 5600, while the sum is 31.

The square root of 21521875 is about 4639.1674899706. The cubic root of 21521875 is about 278.1591613133.

The spelling of 21521875 in words is "twenty-one million, five hundred twenty-one thousand, eight hundred seventy-five".