21728122 has 16 divisors (see below), whose sum is σ = 35176680. Its totient is φ = 10006272.

The previous prime is 21728111. The next prime is 21728129. The reversal of 21728122 is 22182712.

It can be written as a sum of positive squares in 4 ways, for example, as 21613201 + 114921 = 4649^2 + 339^2 .

It is a super-2 number, since 2×21728122² = 944222571293768, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21728129) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20518 + ... + 21550.

Almost surely, 2^21728122 is an apocalyptic number.

21728122 is a deficient number, since it is larger than the sum of its proper divisors (13448558).

21728122 is a wasteful number, since it uses less digits than its factorization.

21728122 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1857.

The product of its digits is 896, while the sum is 25.

The square root of 21728122 is about 4661.3433686009. The cubic root of 21728122 is about 279.0448834323.

The spelling of 21728122 in words is "twenty-one million, seven hundred twenty-eight thousand, one hundred twenty-two".