81772731 has 12 divisors (see below), whose sum is σ = 119286960. Its totient is φ = 53974800.

The previous prime is 81772729. The next prime is 81772739. The reversal of 81772731 is 13727718.

It is a happy number.

It is not a de Polignac number, because 81772731 - 2¹ = 81772729 is a prime.

It is a super-2 number, since 2×81772731² = 13373559070396722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81772739) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 44071 + ... + 45888.

It is an arithmetic number, because the mean of its divisors is an integer number (9940580).

Almost surely, 2^81772731 is an apocalyptic number.

81772731 is a deficient number, since it is larger than the sum of its proper divisors (37514229).

81772731 is a wasteful number, since it uses less digits than its factorization.

81772731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90066 (or 90063 counting only the distinct ones).

The product of its digits is 16464, while the sum is 36.

The square root of 81772731 is about 9042.8275998163. The cubic root of 81772731 is about 434.0464089201.

The spelling of 81772731 in words is "eighty-one million, seven hundred seventy-two thousand, seven hundred thirty-one".