21225870 has 48 divisors (see below), whose sum is σ = 55534752. Its totient is φ = 5624640.

The previous prime is 21225863. The next prime is 21225881. The reversal of 21225870 is 7852212.

21225870 is a nontrivial binomial coefficient, being equal to C(6516, 2).

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15639 + ... + 16941.

It is an arithmetic number, because the mean of its divisors is an integer number (1156974).

Almost surely, 2^21225870 is an apocalyptic number.

21225870 is the 6515-th triangular number and also the 3258-th hexagonal number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21225870, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27767376).

21225870 is an abundant number, since it is smaller than the sum of its proper divisors (34308882).

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

21225870 is a wasteful number, since it uses less digits than its factorization.

21225870 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1497 (or 1494 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 21225870 is about 4607.1542192551. The cubic root of 21225870 is about 276.8780323814.

The spelling of 21225870 in words is "twenty-one million, two hundred twenty-five thousand, eight hundred seventy".