21550356 has 72 divisors (see below), whose sum is σ = 60225984. Its totient is φ = 6462720.

The previous prime is 21550337. The next prime is 21550357. The reversal of 21550356 is 65305512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21550357) 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, 13311 + ... + 14841.

It is an arithmetic number, because the mean of its divisors is an integer number (836472).

Almost surely, 2^21550356 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 21550356, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30112992).

21550356 is an abundant number, since it is smaller than the sum of its proper divisors (38675628).

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

21550356 is a wasteful number, since it uses less digits than its factorization.

21550356 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1581 (or 1576 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 27.

The square root of 21550356 is about 4642.2360991229. The cubic root of 21550356 is about 278.2818079848.

Adding to 21550356 its reverse (65305512), we get a palindrome (86855868).

The spelling of 21550356 in words is "twenty-one million, five hundred fifty thousand, three hundred fifty-six".