81509769 has 24 divisors (see below), whose sum is σ = 134027712. Its totient is φ = 47250720.

The previous prime is 81509759. The next prime is 81509783. The reversal of 81509769 is 96790518.

81509769 is a `hidden beast` number, since 81 + 509 + 7 + 69 = 666.

It is not a de Polignac number, because 81509769 - 2⁵ = 81509737 is a prime.

It is a super-2 number, since 2×81509769² = 13287684884866722, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81509759) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15622 + ... + 20175.

It is an arithmetic number, because the mean of its divisors is an integer number (5584488).

Almost surely, 2^81509769 is an apocalyptic number.

It is an amenable number.

81509769 is a deficient number, since it is larger than the sum of its proper divisors (52517943).

81509769 is a wasteful number, since it uses less digits than its factorization.

81509769 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35837 (or 35834 counting only the distinct ones).

The product of its (nonzero) digits is 136080, while the sum is 45.

The square root of 81509769 is about 9028.2760812904. The cubic root of 81509769 is about 433.5806453493.

The spelling of 81509769 in words is "eighty-one million, five hundred nine thousand, seven hundred sixty-nine".