21057825 has 12 divisors (see below), whose sum is σ = 34815728. Its totient is φ = 11230800.

The previous prime is 21057821. The next prime is 21057877. The reversal of 21057825 is 52875012.

It is not a de Polignac number, because 21057825 - 2² = 21057821 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21057792 and 21057801.

It is not an unprimeable number, because it can be changed into a prime (21057821) 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, 140311 + ... + 140460.

Almost surely, 2^21057825 is an apocalyptic number.

21057825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21057825 is a deficient number, since it is larger than the sum of its proper divisors (13757903).

21057825 is a wasteful number, since it uses less digits than its factorization.

21057825 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280784 (or 280779 counting only the distinct ones).

The product of its (nonzero) digits is 5600, while the sum is 30.

The square root of 21057825 is about 4588.8805824515. The cubic root of 21057825 is about 276.1454153904.

The spelling of 21057825 in words is "twenty-one million, fifty-seven thousand, eight hundred twenty-five".