21553356 has 48 divisors (see below), whose sum is σ = 55157760. Its totient is φ = 6496320.

The previous prime is 21553319. The next prime is 21553361. The reversal of 21553356 is 65335512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35205 + ... + 35811.

It is an arithmetic number, because the mean of its divisors is an integer number (1149120).

Almost surely, 2^21553356 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21553356, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27578880).

21553356 is an abundant number, since it is smaller than the sum of its proper divisors (33604404).

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

21553356 is a wasteful number, since it uses less digits than its factorization.

21553356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 894 (or 892 counting only the distinct ones).

The product of its digits is 13500, while the sum is 30.

The square root of 21553356 is about 4642.5592080231. The cubic root of 21553356 is about 278.2947204813.

Adding to 21553356 its reverse (65335512), we get a palindrome (86888868).

The spelling of 21553356 in words is "twenty-one million, five hundred fifty-three thousand, three hundred fifty-six".