21386765 has 8 divisors (see below), whose sum is σ = 27173880. Its totient is φ = 16102912.

The previous prime is 21386759. The next prime is 21386773. The reversal of 21386765 is 56768312.

It can be written as a sum of positive squares in 4 ways, for example, as 6901129 + 14485636 = 2627^2 + 3806^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21386765 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 7 ways as a sum of consecutive naturals, for example, 125720 + ... + 125889.

It is an arithmetic number, because the mean of its divisors is an integer number (3396735).

Almost surely, 2^21386765 is an apocalyptic number.

It is an amenable number.

21386765 is a deficient number, since it is larger than the sum of its proper divisors (5787115).

21386765 is a wasteful number, since it uses less digits than its factorization.

21386765 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 251631.

The product of its digits is 60480, while the sum is 38.

The square root of 21386765 is about 4624.5826838754. The cubic root of 21386765 is about 277.5758632506.

The spelling of 21386765 in words is "twenty-one million, three hundred eighty-six thousand, seven hundred sixty-five".