21305634 has 32 divisors (see below), whose sum is σ = 49372800. Its totient is φ = 6003072.

The previous prime is 21305611. The next prime is 21305639. The reversal of 21305634 is 43650312.

It is a happy number.

It is a house number.

It is not an unprimeable number, because it can be changed into a prime (21305639) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 409 + ... + 6540.

It is an arithmetic number, because the mean of its divisors is an integer number (1542900).

Almost surely, 2^21305634 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21305634, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24686400).

21305634 is an abundant number, since it is smaller than the sum of its proper divisors (28067166).

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

21305634 is a wasteful number, since it uses less digits than its factorization.

21305634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7034.

The product of its (nonzero) digits is 2160, while the sum is 24.

The square root of 21305634 is about 4615.8026387618. The cubic root of 21305634 is about 277.2244224696.

Adding to 21305634 its reverse (43650312), we get a palindrome (64955946).

The spelling of 21305634 in words is "twenty-one million, three hundred five thousand, six hundred thirty-four".