72309721 has 12 divisors (see below), whose sum is σ = 84158676. Its totient is φ = 61867520.

The previous prime is 72309719. The next prime is 72309733. The reversal of 72309721 is 12790327.

It can be written as a sum of positive squares in 2 ways, for example, as 21344400 + 50965321 = 4620^2 + 7139^2 .

It is not a de Polignac number, because 72309721 - 2¹ = 72309719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72309781) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 15520 + ... + 19633.

It is an arithmetic number, because the mean of its divisors is an integer number (7013223).

Almost surely, 2^72309721 is an apocalyptic number.

It is an amenable number.

72309721 is a deficient number, since it is larger than the sum of its proper divisors (11848955).

72309721 is a wasteful number, since it uses less digits than its factorization.

72309721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35192 (or 35181 counting only the distinct ones).

The product of its (nonzero) digits is 5292, while the sum is 31.

The square root of 72309721 is about 8503.5122743488. The cubic root of 72309721 is about 416.6124350395.

The spelling of 72309721 in words is "seventy-two million, three hundred nine thousand, seven hundred twenty-one".