21553212 has 24 divisors (see below), whose sum is σ = 53249616. Its totient is φ = 6761728.

The previous prime is 21553183. The next prime is 21553223. The reversal of 21553212 is 21235512.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 52623 + ... + 53030.

It is an arithmetic number, because the mean of its divisors is an integer number (2218734).

Almost surely, 2^21553212 is an apocalyptic number.

It is an amenable number.

21553212 is an abundant number, since it is smaller than the sum of its proper divisors (31696404).

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

21553212 is a wasteful number, since it uses less digits than its factorization.

21553212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105677 (or 105675 counting only the distinct ones).

The product of its digits is 600, while the sum is 21.

The square root of 21553212 is about 4642.5436993097. The cubic root of 21553212 is about 278.2941007088.

Adding to 21553212 its reverse (21235512), we get a palindrome (42788724).

The spelling of 21553212 in words is "twenty-one million, five hundred fifty-three thousand, two hundred twelve".