81660213900 has 216 divisors, whose sum is σ = 257915409024. Its totient is φ = 21610368000.

The previous prime is 81660213889. The next prime is 81660213913. The reversal of 81660213900 is 931206618.

81660213900 is a `hidden beast` number, since 8 + 16 + 602 + 1 + 39 + 0 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 120620362 + ... + 120621038.

Almost surely, 2^81660213900 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 81660213900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128957704512).

81660213900 is an abundant number, since it is smaller than the sum of its proper divisors (176255195124).

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

81660213900 is a wasteful number, since it uses less digits than its factorization.

81660213900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1521 (or 1511 counting only the distinct ones).

The product of its (nonzero) digits is 15552, while the sum is 36.

The spelling of 81660213900 in words is "eighty-one billion, six hundred sixty million, two hundred thirteen thousand, nine hundred".