81951392040 has 1024 divisors, whose sum is σ = 329204736000. Its totient is φ = 15872163840.

The previous prime is 81951391981. The next prime is 81951392041. The reversal of 81951392040 is 4029315918.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a junction number, because it is equal to n+sod(n) for n = 81951391983 and 81951392001.

It is not an unprimeable number, because it can be changed into a prime (81951392041) by changing a digit.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 589578291 + ... + 589578429.

It is an arithmetic number, because the mean of its divisors is an integer number (321489000).

Almost surely, 2^81951392040 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 81951392040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (164602368000).

81951392040 is an abundant number, since it is smaller than the sum of its proper divisors (247253343960).

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

81951392040 is a wasteful number, since it uses less digits than its factorization.

81951392040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 290 (or 286 counting only the distinct ones).

The product of its (nonzero) digits is 77760, while the sum is 42.

The spelling of 81951392040 in words is "eighty-one billion, nine hundred fifty-one million, three hundred ninety-two thousand, forty".