72221531 has 2 divisors, whose sum is σ = 72221532. Its totient is φ = 72221530.

The previous prime is 72221507. The next prime is 72221533. The reversal of 72221531 is 13512227.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-72221531 is a prime.

It is a super-2 number, since 2×72221531² = 10431899079967922, which contains 22 as substring.

Together with 72221533, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 72221497 and 72221506.

It is not a weakly prime, because it can be changed into another prime (72221533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36110765 + 36110766.

It is an arithmetic number, because the mean of its divisors is an integer number (36110766).

Almost surely, 2^72221531 is an apocalyptic number.

72221531 is a deficient number, since it is larger than the sum of its proper divisors (1).

72221531 is an equidigital number, since it uses as much as digits as its factorization.

72221531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 840, while the sum is 23.

The square root of 72221531 is about 8498.3251879414. The cubic root of 72221531 is about 416.4429972520.

Adding to 72221531 its reverse (13512227), we get a palindrome (85733758).

The spelling of 72221531 in words is "seventy-two million, two hundred twenty-one thousand, five hundred thirty-one".