21705670 has 16 divisors (see below), whose sum is σ = 44651808. Its totient is φ = 7441920.

The previous prime is 21705667. The next prime is 21705679. The reversal of 21705670 is 7650712.

It is a super-2 number, since 2×21705670² = 942272220297800, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705679) 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 7 ways as a sum of consecutive naturals, for example, 154971 + ... + 155110.

It is an arithmetic number, because the mean of its divisors is an integer number (2790738).

Almost surely, 2^21705670 is an apocalyptic number.

21705670 is an abundant number, since it is smaller than the sum of its proper divisors (22946138).

21705670 is a wasteful number, since it uses less digits than its factorization.

21705670 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 310095.

The product of its (nonzero) digits is 2940, while the sum is 28.

The square root of 21705670 is about 4658.9344275274. The cubic root of 21705670 is about 278.9487365294.

The spelling of 21705670 in words is "twenty-one million, seven hundred five thousand, six hundred seventy".