31909450021 has 4 divisors (see below), whose sum is σ = 31909871500. Its totient is φ = 31909028544.

The previous prime is 31909450009. The next prime is 31909450063. The reversal of 31909450021 is 12005490913.

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 1371887521 + 30537562500 = 37039^2 + 174750^2 .

It is a cyclic number.

It is not a de Polignac number, because 31909450021 - 2⁵ = 31909449989 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 (31909450121) 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, 62346 + ... + 260203.

It is an arithmetic number, because the mean of its divisors is an integer number (7977467875).

Almost surely, 2^31909450021 is an apocalyptic number.

It is an amenable number.

31909450021 is a deficient number, since it is larger than the sum of its proper divisors (421479).

31909450021 is an equidigital number, since it uses as much as digits as its factorization.

31909450021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 421478.

The product of its (nonzero) digits is 9720, while the sum is 34.

The spelling of 31909450021 in words is "thirty-one billion, nine hundred nine million, four hundred fifty thousand, twenty-one".