81980920 has 96 divisors (see below), whose sum is σ = 216773280. Its totient is φ = 27820800.

The previous prime is 81980917. The next prime is 81980923. The reversal of 81980920 is 2908918.

It is an interprime number because it is at equal distance from previous prime (81980917) and next prime (81980923).

It is a hoax number, since the sum of its digits (37) coincides with the sum of the digits of its distinct prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 81980920.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81980923) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 295822 + ... + 296098.

It is an arithmetic number, because the mean of its divisors is an integer number (2258055).

Almost surely, 2^81980920 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 81980920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (108386640).

81980920 is an abundant number, since it is smaller than the sum of its proper divisors (134792360).

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

81980920 is a wasteful number, since it uses less digits than its factorization.

81980920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 453 (or 442 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 37.

The square root of 81980920 is about 9054.3315600877. The cubic root of 81980920 is about 434.4144497408.

The spelling of 81980920 in words is "eighty-one million, nine hundred eighty thousand, nine hundred twenty".