21312705 has 8 divisors (see below), whose sum is σ = 34100352. Its totient is φ = 11366768.

The previous prime is 21312677. The next prime is 21312721. The reversal of 21312705 is 50721312.

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

It is a cyclic number.

It is not a de Polignac number, because 21312705 - 2⁵ = 21312673 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 710409 + ... + 710438.

It is an arithmetic number, because the mean of its divisors is an integer number (4262544).

Almost surely, 2^21312705 is an apocalyptic number.

It is an amenable number.

21312705 is a deficient number, since it is larger than the sum of its proper divisors (12787647).

21312705 is a wasteful number, since it uses less digits than its factorization.

21312705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1420855.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21312705 is about 4616.5685308463. The cubic root of 21312705 is about 277.2550878650.

The spelling of 21312705 in words is "twenty-one million, three hundred twelve thousand, seven hundred five".