31991626640 has 80 divisors (see below), whose sum is σ = 75873447360. Its totient is φ = 12541140480.

The previous prime is 31991626603. The next prime is 31991626643. The reversal of 31991626640 is 4662619913.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (31991626643) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1552082 + ... + 1572558.

It is an arithmetic number, because the mean of its divisors is an integer number (948418092).

Almost surely, 2^31991626640 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 31991626640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37936723680).

31991626640 is an abundant number, since it is smaller than the sum of its proper divisors (43881820720).

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

31991626640 is a wasteful number, since it uses less digits than its factorization.

31991626640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20880 (or 20874 counting only the distinct ones).

The product of its (nonzero) digits is 419904, while the sum is 47.

The spelling of 31991626640 in words is "thirty-one billion, nine hundred ninety-one million, six hundred twenty-six thousand, six hundred forty".