81644813990 has 16 divisors (see below), whose sum is σ = 146964190752. Its totient is φ = 32657142144.

The previous prime is 81644813981. The next prime is 81644814001. The reversal of 81644813990 is 9931844618.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 533822 + ... + 669518.

It is an arithmetic number, because the mean of its divisors is an integer number (9185261922).

Almost surely, 2^81644813990 is an apocalyptic number.

81644813990 is a deficient number, since it is larger than the sum of its proper divisors (65319376762).

81644813990 is a wasteful number, since it uses less digits than its factorization.

81644813990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195871.

The product of its (nonzero) digits is 1492992, while the sum is 53.

The spelling of 81644813990 in words is "eighty-one billion, six hundred forty-four million, eight hundred thirteen thousand, nine hundred ninety".