81931033 has 2 divisors, whose sum is σ = 81931034. Its totient is φ = 81931032.

The previous prime is 81931013. The next prime is 81931063. The reversal of 81931033 is 33013918.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 74597769 + 7333264 = 8637^2 + 2708^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81931033 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 81930992 and 81931010.

It is not a weakly prime, because it can be changed into another prime (81931013) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40965516 + 40965517.

It is an arithmetic number, because the mean of its divisors is an integer number (40965517).

Almost surely, 2^81931033 is an apocalyptic number.

It is an amenable number.

81931033 is a deficient number, since it is larger than the sum of its proper divisors (1).

81931033 is an equidigital number, since it uses as much as digits as its factorization.

81931033 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 81931033 is about 9051.5762715673. The cubic root of 81931033 is about 434.3263152862.

The spelling of 81931033 in words is "eighty-one million, nine hundred thirty-one thousand, thirty-three".