20991670 has 16 divisors (see below), whose sum is σ = 43183008. Its totient is φ = 7197120.

The previous prime is 20991653. The next prime is 20991721. The reversal of 20991670 is 7619902.

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, 149871 + ... + 150010.

It is an arithmetic number, because the mean of its divisors is an integer number (2698938).

Almost surely, 2^20991670 is an apocalyptic number.

20991670 is an abundant number, since it is smaller than the sum of its proper divisors (22191338).

20991670 is a wasteful number, since it uses less digits than its factorization.

20991670 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299895.

The product of its (nonzero) digits is 6804, while the sum is 34.

The square root of 20991670 is about 4581.6667272948. Note that the first 3 decimals coincide. The cubic root of 20991670 is about 275.8559337051.

The spelling of 20991670 in words is "twenty million, nine hundred ninety-one thousand, six hundred seventy".