21228079 has 8 divisors (see below), whose sum is σ = 21765168. Its totient is φ = 20697600.

The previous prime is 21228059. The next prime is 21228089. The reversal of 21228079 is 97082212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21228079 - 2⁹ = 21227567 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21228079.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21228049) 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, 5199 + ... + 8335.

It is an arithmetic number, because the mean of its divisors is an integer number (2720646).

Almost surely, 2^21228079 is an apocalyptic number.

21228079 is a deficient number, since it is larger than the sum of its proper divisors (537089).

21228079 is a wasteful number, since it uses less digits than its factorization.

21228079 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3305.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21228079 is about 4607.3939488609. The cubic root of 21228079 is about 276.8876370502.

It can be divided in two parts, 2122 and 8079, that added together give a palindrome (10201).

The spelling of 21228079 in words is "twenty-one million, two hundred twenty-eight thousand, seventy-nine".