81646765 has 8 divisors (see below), whose sum is σ = 99825048. Its totient is φ = 64084800.

The previous prime is 81646739. The next prime is 81646769. The reversal of 81646765 is 56764618.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1687401 + 79959364 = 1299^2 + 8942^2 .

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

It is a de Polignac number, because none of the positive numbers 2^k-81646765 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81646769) 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, 153786 + ... + 154315.

It is an arithmetic number, because the mean of its divisors is an integer number (12478131).

Almost surely, 2^81646765 is an apocalyptic number.

It is an amenable number.

81646765 is a deficient number, since it is larger than the sum of its proper divisors (18178283).

81646765 is a wasteful number, since it uses less digits than its factorization.

81646765 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 308159.

The product of its digits is 241920, while the sum is 43.

The square root of 81646765 is about 9035.8599480072. The cubic root of 81646765 is about 433.8234202053.

The spelling of 81646765 in words is "eighty-one million, six hundred forty-six thousand, seven hundred sixty-five".