81913669 has 2 divisors, whose sum is σ = 81913670. Its totient is φ = 81913668.

The previous prime is 81913627. The next prime is 81913679. The reversal of 81913669 is 96631918.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 68260644 + 13653025 = 8262^2 + 3695^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81913669 is a prime.

It is a super-2 number, since 2×81913669² = 13419698338083122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81913619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40956834 + 40956835.

It is an arithmetic number, because the mean of its divisors is an integer number (40956835).

Almost surely, 2^81913669 is an apocalyptic number.

It is an amenable number.

81913669 is a deficient number, since it is larger than the sum of its proper divisors (1).

81913669 is an equidigital number, since it uses as much as digits as its factorization.

81913669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 43.

The square root of 81913669 is about 9050.6170507872. The cubic root of 81913669 is about 434.2956302303.

The spelling of 81913669 in words is "eighty-one million, nine hundred thirteen thousand, six hundred sixty-nine".