15220921 has 2 divisors, whose sum is σ = 15220922. Its totient is φ = 15220920.

The previous prime is 15220897. The next prime is 15220973. The reversal of 15220921 is 12902251.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14907321 + 313600 = 3861^2 + 560^2 .

It is an emirp because it is prime and its reverse (12902251) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 15220921 - 2⁵ = 15220889 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 15220892 and 15220901.

It is not a weakly prime, because it can be changed into another prime (15220421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7610460 + 7610461.

It is an arithmetic number, because the mean of its divisors is an integer number (7610461).

Almost surely, 2^15220921 is an apocalyptic number.

It is an amenable number.

15220921 is a deficient number, since it is larger than the sum of its proper divisors (1).

15220921 is an equidigital number, since it uses as much as digits as its factorization.

15220921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 360, while the sum is 22.

The square root of 15220921 is about 3901.3998769672. The cubic root of 15220921 is about 247.8260627827.

The spelling of 15220921 in words is "fifteen million, two hundred twenty thousand, nine hundred twenty-one".