21738906 has 48 divisors (see below), whose sum is σ = 55296384. Its totient is φ = 6041952.

The previous prime is 21738901. The next prime is 21738911. The reversal of 21738906 is 60983712.

It is an interprime number because it is at equal distance from previous prime (21738901) and next prime (21738911).

It is not an unprimeable number, because it can be changed into a prime (21738901) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2331 + ... + 6993.

It is an arithmetic number, because the mean of its divisors is an integer number (1152008).

Almost surely, 2^21738906 is an apocalyptic number.

It is a pronic number, being equal to 4662×4663.

It is a practical number, because each smaller number is the sum of distinct divisors of 21738906, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27648192).

21738906 is an abundant number, since it is smaller than the sum of its proper divisors (33557478).

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

21738906 is a wasteful number, since it uses less digits than its factorization.

21738906 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4715 (or 4712 counting only the distinct ones).

The product of its (nonzero) digits is 18144, while the sum is 36.

The square root of 21738906 is about 4662.4999731903. The cubic root of 21738906 is about 279.0910405479.

The spelling of 21738906 in words is "twenty-one million, seven hundred thirty-eight thousand, nine hundred six".