7921981980 has 384 divisors, whose sum is σ = 29973888000. Its totient is φ = 1711964160.

The previous prime is 7921981957. The next prime is 7921982011. The reversal of 7921981980 is 891891297.

It is a Smith number, since the sum of its digits (54) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 1916556 + ... + 1920684.

It is an arithmetic number, because the mean of its divisors is an integer number (78057000).

Almost surely, 2^7921981980 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 7921981980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (14986944000).

7921981980 is an abundant number, since it is smaller than the sum of its proper divisors (22051906020).

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

7921981980 is a wasteful number, since it uses less digits than its factorization.

7921981980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4194 (or 4186 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 54.

The square root of 7921981980 is about 89005.5165706036. The cubic root of 7921981980 is about 1993.4772483151.

The spelling of 7921981980 in words is "seven billion, nine hundred twenty-one million, nine hundred eighty-one thousand, nine hundred eighty".