20661731 has 4 divisors (see below), whose sum is σ = 20703312. Its totient is φ = 20620152.

The previous prime is 20661727. The next prime is 20661763. The reversal of 20661731 is 13716602.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20661731 - 2² = 20661727 is a prime.

It is a super-2 number, since 2×20661731² = 853814255832722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20661731.

It is not an unprimeable number, because it can be changed into a prime (20661131) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20036 + ... + 21041.

It is an arithmetic number, because the mean of its divisors is an integer number (5175828).

Almost surely, 2^20661731 is an apocalyptic number.

20661731 is a deficient number, since it is larger than the sum of its proper divisors (41581).

20661731 is an equidigital number, since it uses as much as digits as its factorization.

20661731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41580.

The product of its (nonzero) digits is 1512, while the sum is 26.

The square root of 20661731 is about 4545.5176822888. The cubic root of 20661731 is about 274.4030289978.

The spelling of 20661731 in words is "twenty million, six hundred sixty-one thousand, seven hundred thirty-one".