81507511621 has 8 divisors (see below), whose sum is σ = 84343438080. Its totient is φ = 78673273392.

The previous prime is 81507511607. The next prime is 81507511663. The reversal of 81507511621 is 12611570518.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81507511621 - 2¹⁵ = 81507478853 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81507512621) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 323425 + ... + 517318.

It is an arithmetic number, because the mean of its divisors is an integer number (10542929760).

Almost surely, 2^81507511621 is an apocalyptic number.

It is an amenable number.

81507511621 is a deficient number, since it is larger than the sum of its proper divisors (2835926459).

81507511621 is a wasteful number, since it uses less digits than its factorization.

81507511621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 844115.

The product of its (nonzero) digits is 16800, while the sum is 37.

The spelling of 81507511621 in words is "eighty-one billion, five hundred seven million, five hundred eleven thousand, six hundred twenty-one".