21291100 has 36 divisors (see below), whose sum is σ = 48215664. Its totient is φ = 8145280.

The previous prime is 21291097. The next prime is 21291113. The reversal of 21291100 is 119212.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2329 + ... + 6928.

It is an arithmetic number, because the mean of its divisors is an integer number (1339324).

Almost surely, 2^21291100 is an apocalyptic number.

21291100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21291100 is an abundant number, since it is smaller than the sum of its proper divisors (26924564).

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

21291100 is a wasteful number, since it uses less digits than its factorization.

21291100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9294 (or 9287 counting only the distinct ones).

The product of its (nonzero) digits is 36, while the sum is 16.

The square root of 21291100 is about 4614.2279961008. The cubic root of 21291100 is about 277.1613703477.

The spelling of 21291100 in words is "twenty-one million, two hundred ninety-one thousand, one hundred".