15221621 has 4 divisors (see below), whose sum is σ = 15318732. Its totient is φ = 15124512.

The previous prime is 15221617. The next prime is 15221629. The reversal of 15221621 is 12612251.

15221621 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12612251 = 53 ⋅237967.

It can be written as a sum of positive squares in 2 ways, for example, as 9394225 + 5827396 = 3065^2 + 2414^2 .

It is a cyclic number.

It is not a de Polignac number, because 15221621 - 2² = 15221617 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15221593 and 15221602.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15221629) 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, 48320 + ... + 48633.

It is an arithmetic number, because the mean of its divisors is an integer number (3829683).

Almost surely, 2^15221621 is an apocalyptic number.

It is an amenable number.

15221621 is a deficient number, since it is larger than the sum of its proper divisors (97111).

15221621 is an equidigital number, since it uses as much as digits as its factorization.

15221621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97110.

The product of its digits is 240, while the sum is 20.

The square root of 15221621 is about 3901.4895873243. The cubic root of 15221621 is about 247.8298618429.

Adding to 15221621 its reverse (12612251), we get a palindrome (27833872).

The spelling of 15221621 in words is "fifteen million, two hundred twenty-one thousand, six hundred twenty-one".