72221561 has 2 divisors, whose sum is σ = 72221562. Its totient is φ = 72221560.

The previous prime is 72221549. The next prime is 72221647. The reversal of 72221561 is 16512227.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 70644025 + 1577536 = 8405^2 + 1256^2 .

It is a cyclic number.

It is not a de Polignac number, because 72221561 - 2⁶ = 72221497 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 72221561.

It is not a weakly prime, because it can be changed into another prime (72221531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 36110780 + 36110781.

It is an arithmetic number, because the mean of its divisors is an integer number (36110781).

Almost surely, 2^72221561 is an apocalyptic number.

It is an amenable number.

72221561 is a deficient number, since it is larger than the sum of its proper divisors (1).

72221561 is an equidigital number, since it uses as much as digits as its factorization.

72221561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 26.

The square root of 72221561 is about 8498.3269529949. The cubic root of 72221561 is about 416.4430549139.

Adding to 72221561 its reverse (16512227), we get a palindrome (88733788).

The spelling of 72221561 in words is "seventy-two million, two hundred twenty-one thousand, five hundred sixty-one".