31720245138 has 64 divisors (see below), whose sum is σ = 71571237120. Its totient is φ = 10411618176.

The previous prime is 31720245121. The next prime is 31720245143. The reversal of 31720245138 is 83154202713.

31720245138 is a `hidden beast` number, since 3 + 172 + 0 + 2 + 451 + 38 = 666.

It is a super-2 number, since 2×31720245138² (a number of 22 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 2544256 + ... + 2556692.

It is an arithmetic number, because the mean of its divisors is an integer number (1118300580).

Almost surely, 2^31720245138 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31720245138, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35785618560).

31720245138 is an abundant number, since it is smaller than the sum of its proper divisors (39850991982).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

31720245138 is a wasteful number, since it uses less digits than its factorization.

31720245138 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13168 (or 13162 counting only the distinct ones).

The product of its (nonzero) digits is 40320, while the sum is 36.

The spelling of 31720245138 in words is "thirty-one billion, seven hundred twenty million, two hundred forty-five thousand, one hundred thirty-eight".