81121766421 has 16 divisors (see below), whose sum is σ = 114915737664. Its totient is φ = 50726202624.

The previous prime is 81121766419. The next prime is 81121766431. The reversal of 81121766421 is 12466712118.

It is not a de Polignac number, because 81121766421 - 2¹ = 81121766419 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81121766421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81121766431) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2699431 + ... + 2729316.

It is an arithmetic number, because the mean of its divisors is an integer number (7182233604).

Almost surely, 2^81121766421 is an apocalyptic number.

It is an amenable number.

81121766421 is a deficient number, since it is larger than the sum of its proper divisors (33793971243).

81121766421 is a wasteful number, since it uses less digits than its factorization.

81121766421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5429060.

The product of its digits is 32256, while the sum is 39.

The spelling of 81121766421 in words is "eighty-one billion, one hundred twenty-one million, seven hundred sixty-six thousand, four hundred twenty-one".