81689033 has 2 divisors, whose sum is σ = 81689034. Its totient is φ = 81689032.

The previous prime is 81688909. The next prime is 81689039. The reversal of 81689033 is 33098618.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 74787904 + 6901129 = 8648^2 + 2627^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81689033 is a prime.

It is a super-2 number, since 2×81689033² = 13346196224950178, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (81689039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40844516 + 40844517.

It is an arithmetic number, because the mean of its divisors is an integer number (40844517).

Almost surely, 2^81689033 is an apocalyptic number.

It is an amenable number.

81689033 is a deficient number, since it is larger than the sum of its proper divisors (1).

81689033 is an equidigital number, since it uses as much as digits as its factorization.

81689033 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 38.

The square root of 81689033 is about 9038.1985483834. The cubic root of 81689033 is about 433.8982698129.

The spelling of 81689033 in words is "eighty-one million, six hundred eighty-nine thousand, thirty-three".