21556290 has 64 divisors (see below), whose sum is σ = 61710336. Its totient is φ = 4711872.

The previous prime is 21556273. The next prime is 21556321. The reversal of 21556290 is 9265512.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a Curzon number.

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, 2599 + ... + 7061.

It is an arithmetic number, because the mean of its divisors is an integer number (964224).

Almost surely, 2^21556290 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21556290, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30855168).

21556290 is an abundant number, since it is smaller than the sum of its proper divisors (40154046).

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

21556290 is a wasteful number, since it uses less digits than its factorization.

21556290 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4503.

The product of its (nonzero) digits is 5400, while the sum is 30.

The square root of 21556290 is about 4642.8751867781. The cubic root of 21556290 is about 278.3073477439.

The spelling of 21556290 in words is "twenty-one million, five hundred fifty-six thousand, two hundred ninety".