21563125 has 10 divisors (see below), whose sum is σ = 26946062. Its totient is φ = 17250000.

The previous prime is 21563117. The next prime is 21563137. The reversal of 21563125 is 52136512.

It can be written as a sum of positive squares in 5 ways, for example, as 7717284 + 13845841 = 2778^2 + 3721^2 .

It is not a de Polignac number, because 21563125 - 2³ = 21563117 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21563125.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 16626 + ... + 17875.

Almost surely, 2^21563125 is an apocalyptic number.

21563125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21563125 is a deficient number, since it is larger than the sum of its proper divisors (5382937).

21563125 is an frugal number, since it uses more digits than its factorization.

21563125 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34521 (or 34506 counting only the distinct ones).

The product of its digits is 1800, while the sum is 25.

The square root of 21563125 is about 4643.6112025018. The cubic root of 21563125 is about 278.3367595723.

Adding to 21563125 its reverse (52136512), we get a palindrome (73699637).

It can be divided in two parts, 2 and 1563125, that multiplied together give a triangular number (3126250 = T₂₅₀₀).

The spelling of 21563125 in words is "twenty-one million, five hundred sixty-three thousand, one hundred twenty-five".