81913619 has 2 divisors, whose sum is σ = 81913620. Its totient is φ = 81913618.

The previous prime is 81913607. The next prime is 81913627. The reversal of 81913619 is 91631918.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81913619 is a prime.

It is a super-4 number, since 4×81913619⁴ (a number of 33 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81913669) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40956809 + 40956810.

It is an arithmetic number, because the mean of its divisors is an integer number (40956810).

Almost surely, 2^81913619 is an apocalyptic number.

81913619 is a deficient number, since it is larger than the sum of its proper divisors (1).

81913619 is an equidigital number, since it uses as much as digits as its factorization.

81913619 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 81913619 is about 9050.6142885442. The cubic root of 81913619 is about 434.2955418658.

The spelling of 81913619 in words is "eighty-one million, nine hundred thirteen thousand, six hundred nineteen".