21213750 has 40 divisors (see below), whose sum is σ = 53026776. Its totient is φ = 5656000.

The previous prime is 21213719. The next prime is 21213781. The reversal of 21213750 is 5731212.

It is an interprime number because it is at equal distance from previous prime (21213719) and next prime (21213781).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 922 + ... + 6578.

Almost surely, 2^21213750 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21213750, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26513388).

21213750 is an abundant number, since it is smaller than the sum of its proper divisors (31813026).

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

21213750 is an equidigital number, since it uses as much as digits as its factorization.

21213750 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5682 (or 5667 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21213750 is about 4605.8386858421. The cubic root of 21213750 is about 276.8253231062.

Adding to 21213750 its reverse (5731212), we get a palindrome (26944962).

The spelling of 21213750 in words is "twenty-one million, two hundred thirteen thousand, seven hundred fifty".