81580186621 has 2 divisors, whose sum is σ = 81580186622. Its totient is φ = 81580186620.

The previous prime is 81580186553. The next prime is 81580186643. The reversal of 81580186621 is 12668108518.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 51978984121 + 29601202500 = 227989^2 + 172050^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81580186621 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81580183621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40790093310 + 40790093311.

It is an arithmetic number, because the mean of its divisors is an integer number (40790093311).

Almost surely, 2^81580186621 is an apocalyptic number.

It is an amenable number.

81580186621 is a deficient number, since it is larger than the sum of its proper divisors (1).

81580186621 is an equidigital number, since it uses as much as digits as its factorization.

81580186621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 184320, while the sum is 46.

The spelling of 81580186621 in words is "eighty-one billion, five hundred eighty million, one hundred eighty-six thousand, six hundred twenty-one".