81990631458 has 42 divisors (see below), whose sum is σ = 184419160779. Its totient is φ = 27326565972.

The previous prime is 81990631451. The next prime is 81990631469. The reversal of 81990631458 is 85413609918.

It can be written as a sum of positive squares in only one way, i.e., 40995315729 + 40995315729 = 202473^2 + 202473^2 .

It is an ABA number since it can be written as A⋅B^A, here for A=2, B=202473.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (81990631451) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 20 ways as a sum of consecutive naturals, for example, 10929793 + ... + 10937291.

Almost surely, 2^81990631458 is an apocalyptic number.

81990631458 is an abundant number, since it is smaller than the sum of its proper divisors (102428529321).

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

81990631458 is an frugal number, since it uses more digits than its factorization.

81990631458 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15018 (or 7504 counting only the distinct ones).

The product of its (nonzero) digits is 1866240, while the sum is 54.

The spelling of 81990631458 in words is "eighty-one billion, nine hundred ninety million, six hundred thirty-one thousand, four hundred fifty-eight".