72440021 has 4 divisors (see below), whose sum is σ = 72740844. Its totient is φ = 72139200.

The previous prime is 72439981. The next prime is 72440033. The reversal of 72440021 is 12004427.

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 26728900 + 45711121 = 5170^2 + 6761^2 .

It is a cyclic number.

It is not a de Polignac number, because 72440021 - 2¹⁸ = 72177877 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 72439975 and 72440002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72440321) 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, 150050 + ... + 150531.

It is an arithmetic number, because the mean of its divisors is an integer number (18185211).

Almost surely, 2^72440021 is an apocalyptic number.

It is an amenable number.

72440021 is a deficient number, since it is larger than the sum of its proper divisors (300823).

72440021 is a wasteful number, since it uses less digits than its factorization.

72440021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 300822.

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 72440021 is about 8511.1703660542. The cubic root of 72440021 is about 416.8625260172.

Adding to 72440021 its reverse (12004427), we get a palindrome (84444448).

The spelling of 72440021 in words is "seventy-two million, four hundred forty thousand, twenty-one".