16221553 has 4 divisors (see below), whose sum is σ = 17175780. Its totient is φ = 15267328.

The previous prime is 16221529. The next prime is 16221563. The reversal of 16221553 is 35512261.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 35512261 = 5471 ⋅6491.

It can be written as a sum of positive squares in 2 ways, for example, as 11607649 + 4613904 = 3407^2 + 2148^2 .

It is a cyclic number.

It is not a de Polignac number, because 16221553 - 2²¹ = 14124401 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16221523) 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, 477088 + ... + 477121.

It is an arithmetic number, because the mean of its divisors is an integer number (4293945).

Almost surely, 2^16221553 is an apocalyptic number.

It is an amenable number.

16221553 is a deficient number, since it is larger than the sum of its proper divisors (954227).

16221553 is an equidigital number, since it uses as much as digits as its factorization.

16221553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 954226.

The product of its digits is 1800, while the sum is 25.

The square root of 16221553 is about 4027.5989125036. The cubic root of 16221553 is about 253.1419628525.

The spelling of 16221553 in words is "sixteen million, two hundred twenty-one thousand, five hundred fifty-three".