21690228 has 48 divisors (see below), whose sum is σ = 58262400. Its totient is φ = 6152064.

The previous prime is 21690223. The next prime is 21690233. The reversal of 21690228 is 82209612.

It is an interprime number because it is at equal distance from previous prime (21690223) and next prime (21690233).

It is a junction number, because it is equal to n+sod(n) for n = 21690195 and 21690204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690223) 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, 11650 + ... + 13382.

It is an arithmetic number, because the mean of its divisors is an integer number (1213800).

Almost surely, 2^21690228 is an apocalyptic number.

21690228 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21690228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29131200).

21690228 is an abundant number, since it is smaller than the sum of its proper divisors (36572172).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21690228 is a wasteful number, since it uses less digits than its factorization.

21690228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1896 (or 1894 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 30.

The square root of 21690228 is about 4657.2768867655. The cubic root of 21690228 is about 278.8825702805.

The spelling of 21690228 in words is "twenty-one million, six hundred ninety thousand, two hundred twenty-eight".