21996405 has 24 divisors (see below), whose sum is σ = 38368512. Its totient is φ = 11657184.

The previous prime is 21996383. The next prime is 21996409. The reversal of 21996405 is 50469912.

21996405 is a `hidden beast` number, since 2 + 1 + 9 + 9 + 640 + 5 = 666.

It is not a de Polignac number, because 21996405 - 2⁷ = 21996277 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21996405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21996409) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6052 + ... + 8978.

It is an arithmetic number, because the mean of its divisors is an integer number (1598688).

Almost surely, 2^21996405 is an apocalyptic number.

It is an amenable number.

21996405 is a deficient number, since it is larger than the sum of its proper divisors (16372107).

21996405 is a wasteful number, since it uses less digits than its factorization.

21996405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3105 (or 3102 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 21996405 is about 4690.0325158788. The cubic root of 21996405 is about 280.1886696108.

The spelling of 21996405 in words is "twenty-one million, nine hundred ninety-six thousand, four hundred five".