21806100 has 54 divisors (see below), whose sum is σ = 68352830. Its totient is φ = 5814720.

The previous prime is 21806089. The next prime is 21806111. The reversal of 21806100 is 160812.

It is an interprime number because it is at equal distance from previous prime (21806089) and next prime (21806111).

It can be written as a sum of positive squares in 3 ways, for example, as 15876 + 21790224 = 126^2 + 4668^2 .

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 11215 + ... + 13014.

Almost surely, 2^21806100 is an apocalyptic number.

21806100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21806100 is an abundant number, since it is smaller than the sum of its proper divisors (46546730).

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

21806100 is a wasteful number, since it uses less digits than its factorization.

21806100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24249 (or 24239 counting only the distinct ones).

The product of its (nonzero) digits is 96, while the sum is 18.

The square root of 21806100 is about 4669.7002045099. The cubic root of 21806100 is about 279.3782974852.

Adding to 21806100 its reverse (160812), we get a palindrome (21966912).

The spelling of 21806100 in words is "twenty-one million, eight hundred six thousand, one hundred".