72311221 has 4 divisors (see below), whose sum is σ = 72460192. Its totient is φ = 72162252.

The previous prime is 72311191. The next prime is 72311233. The reversal of 72311221 is 12211327.

72311221 = T₂₈₃ + T₂₈₄ + ... + T₇₆₉.

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.

It is a cyclic number.

It is not a de Polignac number, because 72311221 - 2¹¹ = 72309173 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 (72311021) 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, 73755 + ... + 74728.

It is an arithmetic number, because the mean of its divisors is an integer number (18115048).

Almost surely, 2^72311221 is an apocalyptic number.

It is an amenable number.

72311221 is a deficient number, since it is larger than the sum of its proper divisors (148971).

72311221 is a wasteful number, since it uses less digits than its factorization.

72311221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 148970.

The product of its digits is 168, while the sum is 19.

The square root of 72311221 is about 8503.6004727409. The cubic root of 72311221 is about 416.6153157694.

Adding to 72311221 its reverse (12211327), we get a palindrome (84522548).

The spelling of 72311221 in words is "seventy-two million, three hundred eleven thousand, two hundred twenty-one".