21102100 has 36 divisors (see below), whose sum is σ = 48489084. Its totient is φ = 7943680.

The previous prime is 21102091. The next prime is 21102101. The reversal of 21102100 is 120112.

It can be written as a sum of positive squares in 6 ways, for example, as 198916 + 20903184 = 446^2 + 4572^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21102101) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4507 + ... + 7906.

It is an arithmetic number, because the mean of its divisors is an integer number (1346919).

Almost surely, 2^21102100 is an apocalyptic number.

21102100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21102100 is an abundant number, since it is smaller than the sum of its proper divisors (27386984).

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

21102100 is a wasteful number, since it uses less digits than its factorization.

21102100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12444 (or 12437 counting only the distinct ones).

The product of its (nonzero) digits is 4, while the sum is 7.

The square root of 21102100 is about 4593.7022106358. The cubic root of 21102100 is about 276.3388158557.

Adding to 21102100 its reverse (120112), we get a palindrome (21222212).

The spelling of 21102100 in words is "twenty-one million, one hundred two thousand, one hundred".