21387705 has 16 divisors (see below), whose sum is σ = 34329984. Its totient is φ = 11370240.

The previous prime is 21387701. The next prime is 21387721. The reversal of 21387705 is 50778312.

It is not a de Polignac number, because 21387705 - 2² = 21387701 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21387701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2940 + ... + 7170.

It is an arithmetic number, because the mean of its divisors is an integer number (2145624).

Almost surely, 2^21387705 is an apocalyptic number.

It is an amenable number.

21387705 is a deficient number, since it is larger than the sum of its proper divisors (12942279).

21387705 is a wasteful number, since it uses less digits than its factorization.

21387705 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4576.

The product of its (nonzero) digits is 11760, while the sum is 33.

The square root of 21387705 is about 4624.6843135505. The cubic root of 21387705 is about 277.5799299010.

The spelling of 21387705 in words is "twenty-one million, three hundred eighty-seven thousand, seven hundred five".