21651234 has 64 divisors (see below), whose sum is σ = 52254720. Its totient is φ = 5899520.

The previous prime is 21651221. The next prime is 21651271. The reversal of 21651234 is 43215612.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 25387 + ... + 26225.

It is an arithmetic number, because the mean of its divisors is an integer number (816480).

Almost surely, 2^21651234 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21651234, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26127360).

21651234 is an abundant number, since it is smaller than the sum of its proper divisors (30603486).

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

21651234 is a wasteful number, since it uses less digits than its factorization.

21651234 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 895.

The product of its digits is 1440, while the sum is 24.

The square root of 21651234 is about 4653.0886516377. The cubic root of 21651234 is about 278.7153479685.

Adding to 21651234 its reverse (43215612), we get a palindrome (64866846).

The spelling of 21651234 in words is "twenty-one million, six hundred fifty-one thousand, two hundred thirty-four".