72021561 has 4 divisors (see below), whose sum is σ = 96028752. Its totient is φ = 48014372.

The previous prime is 72021557. The next prime is 72021563. The reversal of 72021561 is 16512027.

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 72021561 - 2² = 72021557 is a prime.

It is not an unprimeable number, because it can be changed into a prime (72021563) 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, 12003591 + ... + 12003596.

It is an arithmetic number, because the mean of its divisors is an integer number (24007188).

Almost surely, 2^72021561 is an apocalyptic number.

It is an amenable number.

72021561 is a deficient number, since it is larger than the sum of its proper divisors (24007191).

72021561 is a wasteful number, since it uses less digits than its factorization.

72021561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24007190.

The product of its (nonzero) digits is 840, while the sum is 24.

The square root of 72021561 is about 8486.5517732469. The cubic root of 72021561 is about 416.0582870282.

Adding to 72021561 its reverse (16512027), we get a palindrome (88533588).

The spelling of 72021561 in words is "seventy-two million, twenty-one thousand, five hundred sixty-one".