72745221 has 4 divisors (see below), whose sum is σ = 96993632. Its totient is φ = 48496812.

The previous prime is 72745213. The next prime is 72745223. The reversal of 72745221 is 12254727.

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: 12254727 = 3 ⋅4084909.

It is not a de Polignac number, because 72745221 - 2³ = 72745213 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 (72745223) 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, 12124201 + ... + 12124206.

It is an arithmetic number, because the mean of its divisors is an integer number (24248408).

Almost surely, 2^72745221 is an apocalyptic number.

It is an amenable number.

72745221 is a deficient number, since it is larger than the sum of its proper divisors (24248411).

72745221 is a wasteful number, since it uses less digits than its factorization.

72745221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24248410.

The product of its digits is 7840, while the sum is 30.

The square root of 72745221 is about 8529.0809000736. The cubic root of 72745221 is about 417.4471392551.

Adding to 72745221 its reverse (12254727), we get a palindrome (84999948).

The spelling of 72745221 in words is "seventy-two million, seven hundred forty-five thousand, two hundred twenty-one".