81366609408 has 160 divisors (see below), whose sum is σ = 256275740160. Its totient is φ = 22445875200.

The previous prime is 81366609407. The next prime is 81366609419. The reversal of 81366609408 is 80490666318.

It is a super-2 number, since 2×81366609408² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81366609407) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 181333 + ... + 442283.

It is an arithmetic number, because the mean of its divisors is an integer number (1601723376).

Almost surely, 2^81366609408 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 81366609408, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128137870080).

81366609408 is an abundant number, since it is smaller than the sum of its proper divisors (174909130752).

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

81366609408 is a wasteful number, since it uses less digits than its factorization.

81366609408 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 261008 (or 260992 counting only the distinct ones).

The product of its (nonzero) digits is 1492992, while the sum is 51.

The spelling of 81366609408 in words is "eighty-one billion, three hundred sixty-six million, six hundred nine thousand, four hundred eight".