81646561458 has 48 divisors (see below), whose sum is σ = 220551754176. Its totient is φ = 21206898720.

The previous prime is 81646561433. The next prime is 81646561463. The reversal of 81646561458 is 85416564618.

It is a happy number.

81646561458 is a `hidden beast` number, since 8 + 16 + 4 + 6 + 5 + 614 + 5 + 8 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 29452641 + ... + 29455412.

It is an arithmetic number, because the mean of its divisors is an integer number (4594828212).

Almost surely, 2^81646561458 is an apocalyptic number.

81646561458 is an abundant number, since it is smaller than the sum of its proper divisors (138905192718).

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

81646561458 is a wasteful number, since it uses less digits than its factorization.

81646561458 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58908079 (or 58908076 counting only the distinct ones).

The product of its digits is 5529600, while the sum is 54.

The spelling of 81646561458 in words is "eighty-one billion, six hundred forty-six million, five hundred sixty-one thousand, four hundred fifty-eight".