20311813 has 4 divisors (see below), whose sum is σ = 20342668. Its totient is φ = 20280960.

The previous prime is 20311801. The next prime is 20311831. The reversal of 20311813 is 31811302.

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

It can be written as a sum of positive squares in 2 ways, for example, as 7935489 + 12376324 = 2817^2 + 3518^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20311813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20311883) 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, 14418 + ... + 15763.

It is an arithmetic number, because the mean of its divisors is an integer number (5085667).

Almost surely, 2^20311813 is an apocalyptic number.

It is an amenable number.

20311813 is a deficient number, since it is larger than the sum of its proper divisors (30855).

20311813 is an equidigital number, since it uses as much as digits as its factorization.

20311813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30854.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 20311813 is about 4506.8628778786. The cubic root of 20311813 is about 272.8451446817.

It can be divided in two parts, 2031 and 1813, that added together give a square (3844 = 62²).

The spelling of 20311813 in words is "twenty million, three hundred eleven thousand, eight hundred thirteen".