81381031 has 2 divisors, whose sum is σ = 81381032. Its totient is φ = 81381030.

The previous prime is 81381011. The next prime is 81381059. The reversal of 81381031 is 13018318.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81381031 - 2⁷ = 81380903 is a prime.

It is a super-2 number, since 2×81381031² = 13245744413245922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81380987 and 81381005.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (81381011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40690515 + 40690516.

It is an arithmetic number, because the mean of its divisors is an integer number (40690516).

Almost surely, 2^81381031 is an apocalyptic number.

81381031 is a deficient number, since it is larger than the sum of its proper divisors (1).

81381031 is an equidigital number, since it uses as much as digits as its factorization.

81381031 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 81381031 is about 9021.1435527875. The cubic root of 81381031 is about 433.3522567016.

Adding to 81381031 its reverse (13018318), we get a palindrome (94399349).

The spelling of 81381031 in words is "eighty-one million, three hundred eighty-one thousand, thirty-one".