21812406 has 64 divisors (see below), whose sum is σ = 56180736. Its totient is φ = 5479200.

The previous prime is 21812389. The next prime is 21812419. The reversal of 21812406 is 60421812.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 13561 + ... + 15083.

It is an arithmetic number, because the mean of its divisors is an integer number (877824).

Almost surely, 2^21812406 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21812406, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28090368).

21812406 is an abundant number, since it is smaller than the sum of its proper divisors (34368330).

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

21812406 is a wasteful number, since it uses less digits than its factorization.

21812406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1577.

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 21812406 is about 4670.3753596472. The cubic root of 21812406 is about 279.4052255733.

The spelling of 21812406 in words is "twenty-one million, eight hundred twelve thousand, four hundred six".