21372210 has 48 divisors (see below), whose sum is σ = 56346264. Its totient is φ = 5619456.

The previous prime is 21372187. The next prime is 21372227. The reversal of 21372210 is 1227312.

It can be written as a sum of positive squares in 4 ways, for example, as 21261321 + 110889 = 4611^2 + 333^2 .

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4944 + ... + 8196.

Almost surely, 2^21372210 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21372210, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28173132).

21372210 is an abundant number, since it is smaller than the sum of its proper divisors (34974054).

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

21372210 is a wasteful number, since it uses less digits than its factorization.

21372210 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3339 (or 3336 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21372210 is about 4623.0087605368. The cubic root of 21372210 is about 277.5128798502.

Adding to 21372210 its reverse (1227312), we get a palindrome (22599522).

The spelling of 21372210 in words is "twenty-one million, three hundred seventy-two thousand, two hundred ten".