81961956 has 144 divisors (see below), whose sum is σ = 230053824. Its totient is φ = 25474176.

The previous prime is 81961927. The next prime is 81961961. The reversal of 81961956 is 65916918.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1546426 + ... + 1546478.

It is an arithmetic number, because the mean of its divisors is an integer number (1597596).

Almost surely, 2^81961956 is an apocalyptic number.

81961956 is a gapful number since it is divisible by the number (86) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81961956, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (115026912).

81961956 is an abundant number, since it is smaller than the sum of its proper divisors (148091868).

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

81961956 is a wasteful number, since it uses less digits than its factorization.

81961956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 152 (or 138 counting only the distinct ones).

The product of its digits is 116640, while the sum is 45.

The square root of 81961956 is about 9053.2842659446. The cubic root of 81961956 is about 434.3809506008.

The spelling of 81961956 in words is "eighty-one million, nine hundred sixty-one thousand, nine hundred fifty-six".