21557425 has 6 divisors (see below), whose sum is σ = 26731238. Its totient is φ = 17245920.

The previous prime is 21557407. The next prime is 21557447. The reversal of 21557425 is 52475512.

It can be written as a sum of positive squares in 3 ways, for example, as 323761 + 21233664 = 569^2 + 4608^2 .

It is not a de Polignac number, because 21557425 - 2¹¹ = 21555377 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 431124 + ... + 431173.

Almost surely, 2^21557425 is an apocalyptic number.

21557425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21557425 is a deficient number, since it is larger than the sum of its proper divisors (5173813).

21557425 is an equidigital number, since it uses as much as digits as its factorization.

21557425 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 862307 (or 862302 counting only the distinct ones).

The product of its digits is 14000, while the sum is 31.

The square root of 21557425 is about 4642.9974154634. The cubic root of 21557425 is about 278.3122322161.

The spelling of 21557425 in words is "twenty-one million, five hundred fifty-seven thousand, four hundred twenty-five".