81961880 has 256 divisors, whose sum is σ = 261273600. Its totient is φ = 22302720.

The previous prime is 81961871. The next prime is 81961883. The reversal of 81961880 is 8816918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81961883) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 920876 + ... + 920964.

It is an arithmetic number, because the mean of its divisors is an integer number (1020600).

Almost surely, 2^81961880 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 81961880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (130636800).

81961880 is an abundant number, since it is smaller than the sum of its proper divisors (179311720).

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

81961880 is a wasteful number, since it uses less digits than its factorization.

81961880 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154 (or 150 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 41.

The square root of 81961880 is about 9053.2800685718. The cubic root of 81961880 is about 434.3808163395.

The spelling of 81961880 in words is "eighty-one million, nine hundred sixty-one thousand, eight hundred eighty".