21812425 has 12 divisors (see below), whose sum is σ = 27779596. Its totient is φ = 16977600.

The previous prime is 21812419. The next prime is 21812429. The reversal of 21812425 is 52421812.

21812425 = 506² + 507² + ... + 579².

It can be written as a sum of positive squares in 6 ways, for example, as 22201 + 21790224 = 149^2 + 4668^2 .

It is not a de Polignac number, because 21812425 - 2⁹ = 21811913 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21812425.

It is not an unprimeable number, because it can be changed into a prime (21812429) 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, 10866 + ... + 12715.

Almost surely, 2^21812425 is an apocalyptic number.

21812425 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21812425 is a deficient number, since it is larger than the sum of its proper divisors (5967171).

21812425 is a wasteful number, since it uses less digits than its factorization.

21812425 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23628 (or 23623 counting only the distinct ones).

The product of its digits is 1280, while the sum is 25.

The square root of 21812425 is about 4670.3773937445. The cubic root of 21812425 is about 279.4053066999.

The spelling of 21812425 in words is "twenty-one million, eight hundred twelve thousand, four hundred twenty-five".