21386405 has 16 divisors (see below), whose sum is σ = 26193024. Its totient is φ = 16760640.

The previous prime is 21386399. The next prime is 21386429. The reversal of 21386405 is 50468312.

It is not a de Polignac number, because 21386405 - 2⁸ = 21386149 is a prime.

It is a Duffinian number.

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 15 ways as a sum of consecutive naturals, for example, 67307 + ... + 67623.

It is an arithmetic number, because the mean of its divisors is an integer number (1637064).

Almost surely, 2^21386405 is an apocalyptic number.

It is an amenable number.

21386405 is a deficient number, since it is larger than the sum of its proper divisors (4806619).

21386405 is a wasteful number, since it uses less digits than its factorization.

21386405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 556.

The product of its (nonzero) digits is 5760, while the sum is 29.

The square root of 21386405 is about 4624.5437612807. The cubic root of 21386405 is about 277.5743057785.

The spelling of 21386405 in words is "twenty-one million, three hundred eighty-six thousand, four hundred five".