81661731 has 8 divisors (see below), whose sum is σ = 108958800. Its totient is φ = 54402912.

The previous prime is 81661721. The next prime is 81661733. The reversal of 81661731 is 13716618.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81661731 - 2⁹ = 81661219 is a prime.

It is a super-2 number, since 2×81661731² = 13337276619832722, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 81661692 and 81661701.

It is not an unprimeable number, because it can be changed into a prime (81661733) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4140 + ... + 13433.

It is an arithmetic number, because the mean of its divisors is an integer number (13619850).

Almost surely, 2^81661731 is an apocalyptic number.

81661731 is a deficient number, since it is larger than the sum of its proper divisors (27297069).

81661731 is a wasteful number, since it uses less digits than its factorization.

81661731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19125.

The product of its digits is 6048, while the sum is 33.

The square root of 81661731 is about 9036.6880548130. The cubic root of 81661731 is about 433.8499254590.

The spelling of 81661731 in words is "eighty-one million, six hundred sixty-one thousand, seven hundred thirty-one".