21623406 has 80 divisors (see below), whose sum is σ = 53779200. Its totient is φ = 5778864.

The previous prime is 21623389. The next prime is 21623411. The reversal of 21623406 is 60432612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 273675 + ... + 273753.

It is an arithmetic number, because the mean of its divisors is an integer number (672240).

Almost surely, 2^21623406 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21623406, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26889600).

21623406 is an abundant number, since it is smaller than the sum of its proper divisors (32155794).

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

21623406 is an equidigital number, since it uses as much as digits as its factorization.

21623406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 131 (or 110 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 24.

The square root of 21623406 is about 4650.0974183344. The cubic root of 21623406 is about 278.5958872485.

The spelling of 21623406 in words is "twenty-one million, six hundred twenty-three thousand, four hundred six".