81851099400 has 1296 divisors, whose sum is σ = 354736558800. Its totient is φ = 17459608320.

The previous prime is 81851099383. The next prime is 81851099417. The reversal of 81851099400 is 499015818.

81851099400 is a `hidden beast` number, since 8 + 1 + 8 + 510 + 99 + 40 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (81851099383) and next prime (81851099417).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 323 ways as a sum of consecutive naturals, for example, 1221658167 + ... + 1221658233.

Almost surely, 2^81851099400 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 81851099400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (177368279400).

81851099400 is an abundant number, since it is smaller than the sum of its proper divisors (272885459400).

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

81851099400 is a wasteful number, since it uses less digits than its factorization.

81851099400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 140 (or 103 counting only the distinct ones).

The product of its (nonzero) digits is 103680, while the sum is 45.

The spelling of 81851099400 in words is "eighty-one billion, eight hundred fifty-one million, ninety-nine thousand, four hundred".