81248813 has 4 divisors (see below), whose sum is σ = 81267648. Its totient is φ = 81229980.

The previous prime is 81248789. The next prime is 81248819. The reversal of 81248813 is 31884218.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 31884218 = 2 ⋅15942109.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81248813 is a prime.

It is a super-2 number, since 2×81248813² = 13202739227817938, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81248819) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 620 + ... + 12762.

It is an arithmetic number, because the mean of its divisors is an integer number (20316912).

Almost surely, 2^81248813 is an apocalyptic number.

It is an amenable number.

81248813 is a deficient number, since it is larger than the sum of its proper divisors (18835).

81248813 is a wasteful number, since it uses less digits than its factorization.

81248813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18834.

The product of its digits is 12288, while the sum is 35.

The square root of 81248813 is about 9013.8123455062. The cubic root of 81248813 is about 433.1174434790.

It can be divided in two parts, 812 and 48813, that multiplied together give a triangular number (39636156 = T₈₉₀₃).

The spelling of 81248813 in words is "eighty-one million, two hundred forty-eight thousand, eight hundred thirteen".