72581813 has 4 divisors (see below), whose sum is σ = 75737568. Its totient is φ = 69426060.

The previous prime is 72581801. The next prime is 72581833. The reversal of 72581813 is 31818527.

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: 31818527 = 13 ⋅2447579.

It is a cyclic number.

It is not a de Polignac number, because 72581813 - 2⁴ = 72581797 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 (72581833) 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, 1577843 + ... + 1577888.

It is an arithmetic number, because the mean of its divisors is an integer number (18934392).

Almost surely, 2^72581813 is an apocalyptic number.

It is an amenable number.

72581813 is a deficient number, since it is larger than the sum of its proper divisors (3155755).

72581813 is a wasteful number, since it uses less digits than its factorization.

72581813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3155754.

The product of its digits is 13440, while the sum is 35.

The square root of 72581813 is about 8519.4960531712. The cubic root of 72581813 is about 417.1343336317.

The spelling of 72581813 in words is "seventy-two million, five hundred eighty-one thousand, eight hundred thirteen".