15221321 has 2 divisors, whose sum is σ = 15221322. Its totient is φ = 15221320.

The previous prime is 15221293. The next prime is 15221333. The reversal of 15221321 is 12312251.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11999296 + 3222025 = 3464^2 + 1795^2 .

It is a cyclic number.

It is not a de Polignac number, because 15221321 - 2²² = 11027017 is a prime.

It is a super-2 number, since 2×15221321² = 463377225970082, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 15221321.

It is not a weakly prime, because it can be changed into another prime (15221221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7610660 + 7610661.

It is an arithmetic number, because the mean of its divisors is an integer number (7610661).

Almost surely, 2^15221321 is an apocalyptic number.

It is an amenable number.

15221321 is a deficient number, since it is larger than the sum of its proper divisors (1).

15221321 is an equidigital number, since it uses as much as digits as its factorization.

15221321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 120, while the sum is 17.

The square root of 15221321 is about 3901.4511402810. The cubic root of 15221321 is about 247.8282336885.

Adding to 15221321 its reverse (12312251), we get a palindrome (27533572).

The spelling of 15221321 in words is "fifteen million, two hundred twenty-one thousand, three hundred twenty-one".