31661239639 has 2 divisors, whose sum is σ = 31661239640. Its totient is φ = 31661239638.

The previous prime is 31661239633. The next prime is 31661239669. The reversal of 31661239639 is 93693216613.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 31661239639 - 2¹³ = 31661231447 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 31661239592 and 31661239601.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (31661239633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 15830619819 + 15830619820.

It is an arithmetic number, because the mean of its divisors is an integer number (15830619820).

Almost surely, 2^31661239639 is an apocalyptic number.

31661239639 is a deficient number, since it is larger than the sum of its proper divisors (1).

31661239639 is an equidigital number, since it uses as much as digits as its factorization.

31661239639 is an evil number, because the sum of its binary digits is even.

The product of its digits is 944784, while the sum is 49.

The spelling of 31661239639 in words is "thirty-one billion, six hundred sixty-one million, two hundred thirty-nine thousand, six hundred thirty-nine".