21213900 has 144 divisors (see below), whose sum is σ = 69752480. Its totient is φ = 5598720.

The previous prime is 21213893. The next prime is 21213901. The reversal of 21213900 is 931212.

It is a happy number.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213901) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 218652 + ... + 218748.

Almost surely, 2^21213900 is an apocalyptic number.

21213900 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21213900, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34876240).

21213900 is an abundant number, since it is smaller than the sum of its proper divisors (48538580).

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

21213900 is an equidigital number, since it uses as much as digits as its factorization.

21213900 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 132 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 108, while the sum is 18.

The square root of 21213900 is about 4605.8549694926. The cubic root of 21213900 is about 276.8259755714.

The spelling of 21213900 in words is "twenty-one million, two hundred thirteen thousand, nine hundred".