21400605 has 40 divisors (see below), whose sum is σ = 39125592. Its totient is φ = 11187072.

The previous prime is 21400597. The next prime is 21400667. The reversal of 21400605 is 50600412.

It is a happy number.

21400605 is a `hidden beast` number, since 21 + 40 + 0 + 605 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 7584516 + 13816089 = 2754^2 + 3717^2 .

It is not a de Polignac number, because 21400605 - 2³ = 21400597 is a prime.

It is a congruent 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 39 ways as a sum of consecutive naturals, for example, 20967 + ... + 21963.

Almost surely, 2^21400605 is an apocalyptic number.

It is an amenable number.

21400605 is a deficient number, since it is larger than the sum of its proper divisors (17724987).

21400605 is an equidigital number, since it uses as much as digits as its factorization.

21400605 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1067 (or 1058 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21400605 is about 4626.0787931033. The cubic root of 21400605 is about 277.6357261544.

The spelling of 21400605 in words is "twenty-one million, four hundred thousand, six hundred five".