20731321 has 8 divisors (see below), whose sum is σ = 22748040. Its totient is φ = 18774912.

The previous prime is 20731309. The next prime is 20731327. The reversal of 20731321 is 12313702.

It can be written as a sum of positive squares in 4 ways, for example, as 1904400 + 18826921 = 1380^2 + 4339^2 .

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

It is not a de Polignac number, because 20731321 - 2²¹ = 18634169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20731327) 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, 14356 + ... + 15733.

It is an arithmetic number, because the mean of its divisors is an integer number (2843505).

Almost surely, 2^20731321 is an apocalyptic number.

It is an amenable number.

20731321 is a deficient number, since it is larger than the sum of its proper divisors (2016719).

20731321 is a wasteful number, since it uses less digits than its factorization.

20731321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30155.

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 20731321 is about 4553.1660413387. The cubic root of 20731321 is about 274.7107526231.

The spelling of 20731321 in words is "twenty million, seven hundred thirty-one thousand, three hundred twenty-one".