81391619 has 2 divisors, whose sum is σ = 81391620. Its totient is φ = 81391618.

The previous prime is 81391579. The next prime is 81391669. The reversal of 81391619 is 91619318.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81391619 - 2⁸ = 81391363 is a prime.

It is a super-2 number, since 2×81391619² = 13249191286882322, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81391669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40695809 + 40695810.

It is an arithmetic number, because the mean of its divisors is an integer number (40695810).

Almost surely, 2^81391619 is an apocalyptic number.

81391619 is a deficient number, since it is larger than the sum of its proper divisors (1).

81391619 is an equidigital number, since it uses as much as digits as its factorization.

81391619 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11664, while the sum is 38.

The square root of 81391619 is about 9021.7303772613. The cubic root of 81391619 is about 433.3710495114.

The spelling of 81391619 in words is "eighty-one million, three hundred ninety-one thousand, six hundred nineteen".