81861699690 has 192 divisors, whose sum is σ = 237525949440. Its totient is φ = 19472348160.

The previous prime is 81861699679. The next prime is 81861699739. The reversal of 81861699690 is 9699616818.

81861699690 is a `hidden beast` number, since 8 + 1 + 8 + 616 + 9 + 9 + 6 + 9 + 0 = 666.

It is a super-2 number, since 2×81861699690² (a number of 23 digits) contains 22 as substring.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1940502 + ... + 1982238.

It is an arithmetic number, because the mean of its divisors is an integer number (1237114320).

Almost surely, 2^81861699690 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81861699690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118762974720).

81861699690 is an abundant number, since it is smaller than the sum of its proper divisors (155664249750).

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

81861699690 is a wasteful number, since it uses less digits than its factorization.

81861699690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41837 (or 41834 counting only the distinct ones).

The product of its (nonzero) digits is 10077696, while the sum is 63.

The spelling of 81861699690 in words is "eighty-one billion, eight hundred sixty-one million, six hundred ninety-nine thousand, six hundred ninety".