21017925 has 36 divisors (see below), whose sum is σ = 38035140. Its totient is φ = 11093760.

The previous prime is 21017897. The next prime is 21017951. The reversal of 21017925 is 52971012.

It can be written as a sum of positive squares in 6 ways, for example, as 956484 + 20061441 = 978^2 + 4479^2 .

It is not a de Polignac number, because 21017925 - 2⁶ = 21017861 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 24097 + ... + 24953.

Almost surely, 2^21017925 is an apocalyptic number.

21017925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21017925 is a deficient number, since it is larger than the sum of its proper divisors (17017215).

21017925 is a wasteful number, since it uses less digits than its factorization.

21017925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 982 (or 974 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21017925 is about 4584.5310556261. The cubic root of 21017925 is about 275.9708932758.

Adding to 21017925 its reverse (52971012), we get a palindrome (73988937).

The spelling of 21017925 in words is "twenty-one million, seventeen thousand, nine hundred twenty-five".