81731269 has 4 divisors (see below), whose sum is σ = 81751680. Its totient is φ = 81710860.

The previous prime is 81731239. The next prime is 81731329. The reversal of 81731269 is 96213718.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81731269 is a prime.

It is a super-2 number, since 2×81731269² = 13360000664700722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81731239) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1999 + ... + 12940.

It is an arithmetic number, because the mean of its divisors is an integer number (20437920).

Almost surely, 2^81731269 is an apocalyptic number.

It is an amenable number.

81731269 is a deficient number, since it is larger than the sum of its proper divisors (20411).

81731269 is a wasteful number, since it uses less digits than its factorization.

81731269 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20410.

The product of its digits is 18144, while the sum is 37.

The square root of 81731269 is about 9040.5347740054. The cubic root of 81731269 is about 433.9730369680.

The spelling of 81731269 in words is "eighty-one million, seven hundred thirty-one thousand, two hundred sixty-nine".