72781817 has 4 divisors (see below), whose sum is σ = 72799860. Its totient is φ = 72763776.

The previous prime is 72781783. The next prime is 72781829. The reversal of 72781817 is 71818727.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 42981136 + 29800681 = 6556^2 + 5459^2 .

It is a cyclic number.

It is not a de Polignac number, because 72781817 - 2¹⁰ = 72780793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72781117) 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, 113 + ... + 12065.

It is an arithmetic number, because the mean of its divisors is an integer number (18199965).

Almost surely, 2^72781817 is an apocalyptic number.

It is an amenable number.

72781817 is a deficient number, since it is larger than the sum of its proper divisors (18043).

72781817 is a wasteful number, since it uses less digits than its factorization.

72781817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18042.

The product of its digits is 43904, while the sum is 41.

The square root of 72781817 is about 8531.2259963032. The cubic root of 72781817 is about 417.5171293485.

The spelling of 72781817 in words is "seventy-two million, seven hundred eighty-one thousand, eight hundred seventeen".