81117919 has 2 divisors, whose sum is σ = 81117920. Its totient is φ = 81117918.

The previous prime is 81117851. The next prime is 81117923. The reversal of 81117919 is 91971118.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 81117919 - 2⁷ = 81117791 is a prime.

It is a super-2 number, since 2×81117919² = 13160233565781122, which contains 22 as substring.

It is equal to p_4730995 and since 81117919 and 4730995 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81117989) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40558959 + 40558960.

It is an arithmetic number, because the mean of its divisors is an integer number (40558960).

Almost surely, 2^81117919 is an apocalyptic number.

81117919 is a deficient number, since it is larger than the sum of its proper divisors (1).

81117919 is an equidigital number, since it uses as much as digits as its factorization.

81117919 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4536, while the sum is 37.

The square root of 81117919 is about 9006.5486730490. The cubic root of 81117919 is about 432.8847305560.

The spelling of 81117919 in words is "eighty-one million, one hundred seventeen thousand, nine hundred nineteen".