991660607980 has 192 divisors, whose sum is σ = 2531051857152. Its totient is φ = 318596382720.

The previous prime is 991660607947. The next prime is 991660608011. The reversal of 991660607980 is 89706066199.

991660607980 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a super-2 number, since 2×991660607980² (a number of 25 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 978933954 + ... + 978934966.

It is an arithmetic number, because the mean of its divisors is an integer number (13182561756).

Almost surely, 2^991660607980 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 991660607980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1265525928576).

991660607980 is an abundant number, since it is smaller than the sum of its proper divisors (1539391249172).

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

991660607980 is a wasteful number, since it uses less digits than its factorization.

991660607980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2444 (or 2442 counting only the distinct ones).

The product of its (nonzero) digits is 8817984, while the sum is 61.

The spelling of 991660607980 in words is "nine hundred ninety-one billion, six hundred sixty million, six hundred seven thousand, nine hundred eighty".