81577919 has 2 divisors, whose sum is σ = 81577920. Its totient is φ = 81577918.

The previous prime is 81577907. The next prime is 81577921. The reversal of 81577919 is 91977518.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81577919 - 2²⁰ = 80529343 is a prime.

It is a super-2 number, since 2×81577919² = 13309913736741122, which contains 22 as substring.

Together with 81577921, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81577949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40788959 + 40788960.

It is an arithmetic number, because the mean of its divisors is an integer number (40788960).

Almost surely, 2^81577919 is an apocalyptic number.

81577919 is a deficient number, since it is larger than the sum of its proper divisors (1).

81577919 is an equidigital number, since it uses as much as digits as its factorization.

81577919 is an evil number, because the sum of its binary digits is even.

The product of its digits is 158760, while the sum is 47.

The square root of 81577919 is about 9032.0495459226. The cubic root of 81577919 is about 433.7014500496.

The spelling of 81577919 in words is "eighty-one million, five hundred seventy-seven thousand, nine hundred nineteen".