81661101575 has 6 divisors (see below), whose sum is σ = 101259765984. Its totient is φ = 65328881240.

The previous prime is 81661101569. The next prime is 81661101581. The reversal of 81661101575 is 57510116618.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81661101569) and next prime (81661101581).

It is not a de Polignac number, because 81661101575 - 2⁴ = 81661101559 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1633222007 + ... + 1633222056.

It is an arithmetic number, because the mean of its divisors is an integer number (16876627664).

Almost surely, 2^81661101575 is an apocalyptic number.

81661101575 is a deficient number, since it is larger than the sum of its proper divisors (19598664409).

81661101575 is a wasteful number, since it uses less digits than its factorization.

81661101575 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3266444073 (or 3266444068 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 41.

The spelling of 81661101575 in words is "eighty-one billion, six hundred sixty-one million, one hundred one thousand, five hundred seventy-five".