72217021 has 4 divisors (see below), whose sum is σ = 72254944. Its totient is φ = 72179100.

The previous prime is 72217001. The next prime is 72217027. The reversal of 72217021 is 12071227.

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 72217021 - 2⁹ = 72216509 is a prime.

It is a super-2 number, since 2×72217021² = 10430596244228882, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 72216983 and 72217001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72217027) 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, 15945 + ... + 19966.

It is an arithmetic number, because the mean of its divisors is an integer number (18063736).

Almost surely, 2^72217021 is an apocalyptic number.

It is an amenable number.

72217021 is a deficient number, since it is larger than the sum of its proper divisors (37923).

72217021 is a wasteful number, since it uses less digits than its factorization.

72217021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37922.

The product of its (nonzero) digits is 392, while the sum is 22.

The square root of 72217021 is about 8498.0598373982. The cubic root of 72217021 is about 416.4343285675.

Adding to 72217021 its reverse (12071227), we get a palindrome (84288248).

The spelling of 72217021 in words is "seventy-two million, two hundred seventeen thousand, twenty-one".