21220056 has 160 divisors (see below), whose sum is σ = 70131600. Its totient is φ = 5909760.

The previous prime is 21220019. The next prime is 21220103. The reversal of 21220056 is 65002212.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 92550 + ... + 92778.

Almost surely, 2^21220056 is an apocalyptic number.

21220056 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21220056, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35065800).

21220056 is an abundant number, since it is smaller than the sum of its proper divisors (48911544).

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

21220056 is a wasteful number, since it uses less digits than its factorization.

21220056 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271 (or 258 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 21220056 is about 4606.5232008533. The cubic root of 21220056 is about 276.8527500902.

Adding to 21220056 its reverse (65002212), we get a palindrome (86222268).

The spelling of 21220056 in words is "twenty-one million, two hundred twenty thousand, fifty-six".