20931745 has 16 divisors (see below), whose sum is σ = 25618320. Its totient is φ = 16416000.

The previous prime is 20931739. The next prime is 20931773. The reversal of 20931745 is 54713902.

It can be written as a sum of positive squares in 8 ways, for example, as 419904 + 20511841 = 648^2 + 4529^2 .

It is a de Polignac number, because none of the positive numbers 2^k-20931745 is a prime.

It is an unprimeable number.

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, 91291 + ... + 91519.

It is an arithmetic number, because the mean of its divisors is an integer number (1601145).

Almost surely, 2^20931745 is an apocalyptic number.

It is an amenable number.

20931745 is a deficient number, since it is larger than the sum of its proper divisors (4686575).

20931745 is a wasteful number, since it uses less digits than its factorization.

20931745 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 516.

The product of its (nonzero) digits is 7560, while the sum is 31.

The square root of 20931745 is about 4575.1224027342. The cubic root of 20931745 is about 275.5931878656.

The spelling of 20931745 in words is "twenty million, nine hundred thirty-one thousand, seven hundred forty-five".