21706905 has 32 divisors (see below), whose sum is σ = 38102400. Its totient is φ = 10465280.

The previous prime is 21706897. The next prime is 21706921. The reversal of 21706905 is 50960712.

It is not a de Polignac number, because 21706905 - 2³ = 21706897 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 48121 + ... + 48569.

It is an arithmetic number, because the mean of its divisors is an integer number (1190700).

Almost surely, 2^21706905 is an apocalyptic number.

It is an amenable number.

21706905 is a deficient number, since it is larger than the sum of its proper divisors (16395495).

21706905 is a wasteful number, since it uses less digits than its factorization.

21706905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 761.

The product of its (nonzero) digits is 3780, while the sum is 30.

The square root of 21706905 is about 4659.0669666791. The cubic root of 21706905 is about 278.9540269313.

The spelling of 21706905 in words is "twenty-one million, seven hundred six thousand, nine hundred five".