81116542621 has 2 divisors, whose sum is σ = 81116542622. Its totient is φ = 81116542620.

The previous prime is 81116542609. The next prime is 81116542681. The reversal of 81116542621 is 12624561118.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 80989191396 + 127351225 = 284586^2 + 11285^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81116542621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81116542601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40558271310 + 40558271311.

It is an arithmetic number, because the mean of its divisors is an integer number (40558271311).

Almost surely, 2^81116542621 is an apocalyptic number.

It is an amenable number.

81116542621 is a deficient number, since it is larger than the sum of its proper divisors (1).

81116542621 is an equidigital number, since it uses as much as digits as its factorization.

81116542621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23040, while the sum is 37.

The spelling of 81116542621 in words is "eighty-one billion, one hundred sixteen million, five hundred forty-two thousand, six hundred twenty-one".