81639257610 has 32 divisors (see below), whose sum is σ = 197107489152. Its totient is φ = 21640105280.

The previous prime is 81639257591. The next prime is 81639257633. The reversal of 81639257610 is 1675293618.

It is a super-2 number, since 2×81639257610² (a number of 23 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81639257610.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8142621 + ... + 8152640.

It is an arithmetic number, because the mean of its divisors is an integer number (6159609036).

Almost surely, 2^81639257610 is an apocalyptic number.

81639257610 is an abundant number, since it is smaller than the sum of its proper divisors (115468231542).

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

81639257610 is a wasteful number, since it uses less digits than its factorization.

81639257610 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16295438.

The product of its (nonzero) digits is 544320, while the sum is 48.

The spelling of 81639257610 in words is "eighty-one billion, six hundred thirty-nine million, two hundred fifty-seven thousand, six hundred ten".