21421525 has 12 divisors (see below), whose sum is σ = 27181792. Its totient is φ = 16737840.

The previous prime is 21421489. The next prime is 21421537. The reversal of 21421525 is 52512412.

It is not a de Polignac number, because 21421525 - 2⁷ = 21421397 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21421496 and 21421505.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8889 + ... + 11038.

Almost surely, 2^21421525 is an apocalyptic number.

21421525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21421525 is a deficient number, since it is larger than the sum of its proper divisors (5760267).

21421525 is a wasteful number, since it uses less digits than its factorization.

21421525 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19980 (or 19975 counting only the distinct ones).

The product of its digits is 800, while the sum is 22.

The square root of 21421525 is about 4628.3393350099. The cubic root of 21421525 is about 277.7261635953.

Adding to 21421525 its reverse (52512412), we get a palindrome (73933937).

The spelling of 21421525 in words is "twenty-one million, four hundred twenty-one thousand, five hundred twenty-five".