21505925 has 12 divisors (see below), whose sum is σ = 30477216. Its totient is φ = 14746800.

The previous prime is 21505903. The next prime is 21505927. The reversal of 21505925 is 52950512.

It is not a de Polignac number, because 21505925 - 2¹⁶ = 21440389 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21505927) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61271 + ... + 61620.

It is an arithmetic number, because the mean of its divisors is an integer number (2539768).

Almost surely, 2^21505925 is an apocalyptic number.

21505925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21505925 is a deficient number, since it is larger than the sum of its proper divisors (8971291).

21505925 is a wasteful number, since it uses less digits than its factorization.

21505925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 122908 (or 122903 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 29.

The square root of 21505925 is about 4637.4481129173. The cubic root of 21505925 is about 278.0904291500.

The spelling of 21505925 in words is "twenty-one million, five hundred five thousand, nine hundred twenty-five".