21157925 has 12 divisors (see below), whose sum is σ = 27617280. Its totient is φ = 16035120.

The previous prime is 21157921. The next prime is 21157933. The reversal of 21157925 is 52975112.

It is a happy number.

It is not a de Polignac number, because 21157925 - 2² = 21157921 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21157891 and 21157900.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21157921) 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, 21797 + ... + 22746.

It is an arithmetic number, because the mean of its divisors is an integer number (2301440).

Almost surely, 2^21157925 is an apocalyptic number.

21157925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21157925 is a deficient number, since it is larger than the sum of its proper divisors (6459355).

21157925 is a wasteful number, since it uses less digits than its factorization.

21157925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44572 (or 44567 counting only the distinct ones).

The product of its digits is 6300, while the sum is 32.

The square root of 21157925 is about 4599.7744509921. The cubic root of 21157925 is about 276.5822834221.

The spelling of 21157925 in words is "twenty-one million, one hundred fifty-seven thousand, nine hundred twenty-five".