21028099 has 16 divisors (see below), whose sum is σ = 23162976. Its totient is φ = 19008000.

The previous prime is 21028097. The next prime is 21028123. The reversal of 21028099 is 99082012.

It is a cyclic number.

It is not a de Polignac number, because 21028099 - 2¹ = 21028097 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21028099.

It is not an unprimeable number, because it can be changed into a prime (21028093) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 63364 + ... + 63694.

It is an arithmetic number, because the mean of its divisors is an integer number (1447686).

Almost surely, 2^21028099 is an apocalyptic number.

21028099 is a deficient number, since it is larger than the sum of its proper divisors (2134877).

21028099 is a wasteful number, since it uses less digits than its factorization.

21028099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 486.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 21028099 is about 4585.6405223262. The cubic root of 21028099 is about 276.0154151931.

It can be divided in two parts, 2102 and 8099, that added together give a palindrome (10201).

The spelling of 21028099 in words is "twenty-one million, twenty-eight thousand, ninety-nine".