72381521 has 4 divisors (see below), whose sum is σ = 72469872. Its totient is φ = 72293172.

The previous prime is 72381493. The next prime is 72381539. The reversal of 72381521 is 12518327.

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: 12518327 = 31 ⋅403817.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72381521 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (72381571) 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, 42935 + ... + 44588.

It is an arithmetic number, because the mean of its divisors is an integer number (18117468).

Almost surely, 2^72381521 is an apocalyptic number.

It is an amenable number.

72381521 is a deficient number, since it is larger than the sum of its proper divisors (88351).

72381521 is an equidigital number, since it uses as much as digits as its factorization.

72381521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88350.

The product of its digits is 3360, while the sum is 29.

The square root of 72381521 is about 8507.7330117958. The cubic root of 72381521 is about 416.7502813173.

Adding to 72381521 its reverse (12518327), we get a palindrome (84899848).

The spelling of 72381521 in words is "seventy-two million, three hundred eighty-one thousand, five hundred twenty-one".