81278831 has 2 divisors, whose sum is σ = 81278832. Its totient is φ = 81278830.

The previous prime is 81278801. The next prime is 81278837. The reversal of 81278831 is 13887218.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81278831 is a prime.

It is a super-2 number, since 2×81278831² = 13212496737453122, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81278837) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40639415 + 40639416.

It is an arithmetic number, because the mean of its divisors is an integer number (40639416).

Almost surely, 2^81278831 is an apocalyptic number.

81278831 is a deficient number, since it is larger than the sum of its proper divisors (1).

81278831 is an equidigital number, since it uses as much as digits as its factorization.

81278831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21504, while the sum is 38.

The square root of 81278831 is about 9015.4773029496. The cubic root of 81278831 is about 433.1707764370.

The spelling of 81278831 in words is "eighty-one million, two hundred seventy-eight thousand, eight hundred thirty-one".