21205100 has 36 divisors (see below), whose sum is σ = 52590384. Its totient is φ = 7270080.

The previous prime is 21205099. The next prime is 21205109. The reversal of 21205100 is 150212.

It is not an unprimeable number, because it can be changed into a prime (21205109) 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, 14447 + ... + 15846.

It is an arithmetic number, because the mean of its divisors is an integer number (1460844).

Almost surely, 2^21205100 is an apocalyptic number.

21205100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21205100 is an abundant number, since it is smaller than the sum of its proper divisors (31385284).

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

21205100 is a wasteful number, since it uses less digits than its factorization.

21205100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30314 (or 30307 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 21205100 is about 4604.8995645942. The cubic root of 21205100 is about 276.7876924094.

Adding to 21205100 its reverse (150212), we get a palindrome (21355312).

The spelling of 21205100 in words is "twenty-one million, two hundred five thousand, one hundred".