99999999581 has 2 divisors, whose sum is σ = 99999999582. Its totient is φ = 99999999580.

The previous prime is 99999999571. The next prime is 99999999599. The reversal of 99999999581 is 18599999999.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 77525492356 + 22474507225 = 278434^2 + 149915^2 .

It is a cyclic number.

It is not a de Polignac number, because 99999999581 - 2¹⁴ = 99999983197 is a prime.

It is a super-2 number, since 2×99999999581² (a number of 23 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 99999999493 and 99999999502.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (99999999551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 49999999790 + 49999999791.

It is an arithmetic number, because the mean of its divisors is an integer number (49999999791).

Almost surely, 2^99999999581 is an apocalyptic number.

It is an amenable number.

99999999581 is a deficient number, since it is larger than the sum of its proper divisors (1).

99999999581 is an equidigital number, since it uses as much as digits as its factorization.

99999999581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1721868840, while the sum is 86.

The spelling of 99999999581 in words is "ninety-nine billion, nine hundred ninety-nine million, nine hundred ninety-nine thousand, five hundred eighty-one".