81569399 has 2 divisors, whose sum is σ = 81569400. Its totient is φ = 81569398.

The previous prime is 81569357. The next prime is 81569429. The reversal of 81569399 is 99396518.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81569399 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81569599) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40784699 + 40784700.

It is an arithmetic number, because the mean of its divisors is an integer number (40784700).

Almost surely, 2^81569399 is an apocalyptic number.

81569399 is a deficient number, since it is larger than the sum of its proper divisors (1).

81569399 is an equidigital number, since it uses as much as digits as its factorization.

81569399 is an evil number, because the sum of its binary digits is even.

The product of its digits is 524880, while the sum is 50.

The square root of 81569399 is about 9031.5778798613. The cubic root of 81569399 is about 433.6863509270.

The spelling of 81569399 in words is "eighty-one million, five hundred sixty-nine thousand, three hundred ninety-nine".