81971635605 has 16 divisors (see below), whose sum is σ = 133304694144. Its totient is φ = 43001513280.

The previous prime is 81971635573. The next prime is 81971635637. The reversal of 81971635605 is 50653617918.

It is an interprime number because it is at equal distance from previous prime (81971635573) and next prime (81971635637).

It is not a de Polignac number, because 81971635605 - 2⁵ = 81971635573 is a prime.

It is a congruent number.

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, 44792329 + ... + 44794158.

It is an arithmetic number, because the mean of its divisors is an integer number (8331543384).

Almost surely, 2^81971635605 is an apocalyptic number.

It is an amenable number.

81971635605 is a deficient number, since it is larger than the sum of its proper divisors (51333058539).

81971635605 is a wasteful number, since it uses less digits than its factorization.

81971635605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89586556.

The product of its (nonzero) digits is 1360800, while the sum is 51.

The spelling of 81971635605 in words is "eighty-one billion, nine hundred seventy-one million, six hundred thirty-five thousand, six hundred five".