81977980 has 72 divisors (see below), whose sum is σ = 209024928. Its totient is φ = 26877312.

The previous prime is 81977947. The next prime is 81978007. The reversal of 81977980 is 8977918.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20722 + ... + 24358.

It is an arithmetic number, because the mean of its divisors is an integer number (2903124).

Almost surely, 2^81977980 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 81977980, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (104512464).

81977980 is an abundant number, since it is smaller than the sum of its proper divisors (127046948).

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

81977980 is a wasteful number, since it uses less digits than its factorization.

81977980 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3683 (or 3674 counting only the distinct ones).

The product of its (nonzero) digits is 254016, while the sum is 49.

The square root of 81977980 is about 9054.1692053992. The cubic root of 81977980 is about 434.4092566879.

The spelling of 81977980 in words is "eighty-one million, nine hundred seventy-seven thousand, nine hundred eighty".