21890100 has 72 divisors (see below), whose sum is σ = 63933408. Its totient is φ = 5782400.

The previous prime is 21890093. The next prime is 21890107. The reversal of 21890100 is 109812.

It is an interprime number because it is at equal distance from previous prime (21890093) and next prime (21890107).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21890107) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39022 + ... + 39578.

It is an arithmetic number, because the mean of its divisors is an integer number (887964).

Almost surely, 2^21890100 is an apocalyptic number.

21890100 is a gapful number since it is divisible by the number (20) 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 21890100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31966704).

21890100 is an abundant number, since it is smaller than the sum of its proper divisors (42043308).

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

21890100 is a wasteful number, since it uses less digits than its factorization.

21890100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 705 (or 698 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 21.

The square root of 21890100 is about 4678.6857128899. The cubic root of 21890100 is about 279.7365719687.

Adding to 21890100 its reverse (109812), we get a palindrome (21999912).

The spelling of 21890100 in words is "twenty-one million, eight hundred ninety thousand, one hundred".