15920221 has 4 divisors (see below), whose sum is σ = 15928444. Its totient is φ = 15912000.

The previous prime is 15920189. The next prime is 15920237. The reversal of 15920221 is 12202951.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12202951 = 149 ⋅81899.

It can be written as a sum of positive squares in 2 ways, for example, as 8100 + 15912121 = 90^2 + 3989^2 .

It is a cyclic number.

It is not a de Polignac number, because 15920221 - 2⁵ = 15920189 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 15920192 and 15920201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15920251) 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, 571 + ... + 5671.

It is an arithmetic number, because the mean of its divisors is an integer number (3982111).

Almost surely, 2^15920221 is an apocalyptic number.

It is an amenable number.

15920221 is a deficient number, since it is larger than the sum of its proper divisors (8223).

15920221 is an equidigital number, since it uses as much as digits as its factorization.

15920221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8222.

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

The square root of 15920221 is about 3990.0151628785. The cubic root of 15920221 is about 251.5646984441.

The spelling of 15920221 in words is "fifteen million, nine hundred twenty thousand, two hundred twenty-one".