21001100 has 18 divisors (see below), whose sum is σ = 45572604. Its totient is φ = 8400400.

The previous prime is 21001087. The next prime is 21001117. The reversal of 21001100 is 110012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (5).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 104906 + ... + 105105.

Almost surely, 2^21001100 is an apocalyptic number.

21001100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21001100 is an abundant number, since it is smaller than the sum of its proper divisors (24571504).

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

21001100 is a wasteful number, since it uses less digits than its factorization.

21001100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 210025 (or 210018 counting only the distinct ones).

The product of its (nonzero) digits is 2, while the sum is 5.

The square root of 21001100 is about 4582.6957132238. The cubic root of 21001100 is about 275.8972347232.

Adding to 21001100 its reverse (110012), we get a palindrome (21111112).

The spelling of 21001100 in words is "twenty-one million, one thousand, one hundred".