81649752593 has 8 divisors (see below), whose sum is σ = 81884910888. Its totient is φ = 81414681984.

The previous prime is 81649752577. The next prime is 81649752599. The reversal of 81649752593 is 39525794618.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 32159966224 + 49489786369 = 179332^2 + 222463^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 81649752593 - 2⁴ = 81649752577 is a prime.

It is a super-2 number, since 2×81649752593² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81649752599) 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, 2149421 + ... + 2187077.

It is an arithmetic number, because the mean of its divisors is an integer number (10235613861).

Almost surely, 2^81649752593 is an apocalyptic number.

It is an amenable number.

81649752593 is a deficient number, since it is larger than the sum of its proper divisors (235158295).

81649752593 is a wasteful number, since it uses less digits than its factorization.

81649752593 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 43843.

The product of its digits is 16329600, while the sum is 59.

The spelling of 81649752593 in words is "eighty-one billion, six hundred forty-nine million, seven hundred fifty-two thousand, five hundred ninety-three".