20312981 has 8 divisors (see below), whose sum is σ = 21919800. Its totient is φ = 18712512.

The previous prime is 20312959. The next prime is 20312983. The reversal of 20312981 is 18921302.

It can be written as a sum of positive squares in 4 ways, for example, as 152881 + 20160100 = 391^2 + 4490^2 .

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

It is not a de Polignac number, because 20312981 - 2²² = 16118677 is a prime.

It is a super-2 number, since 2×20312981² = 825234394212722, 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 20312981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20312983) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6695 + ... + 9243.

It is an arithmetic number, because the mean of its divisors is an integer number (2739975).

Almost surely, 2^20312981 is an apocalyptic number.

It is an amenable number.

20312981 is a deficient number, since it is larger than the sum of its proper divisors (1606819).

20312981 is a wasteful number, since it uses less digits than its factorization.

20312981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3175.

The product of its (nonzero) digits is 864, while the sum is 26.

The square root of 20312981 is about 4506.9924561730. The cubic root of 20312981 is about 272.8503744302.

The spelling of 20312981 in words is "twenty million, three hundred twelve thousand, nine hundred eighty-one".