21552318 has 20 divisors (see below), whose sum is σ = 48293520. Its totient is φ = 7184052.

The previous prime is 21552317. The next prime is 21552319. The reversal of 21552318 is 81325512.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21552317) and next prime (21552319).

It is a super-3 number, since 3×21552318³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21552291 and 21552300.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21552317) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 66358 + ... + 66681.

It is an arithmetic number, because the mean of its divisors is an integer number (2414676).

Almost surely, 2^21552318 is an apocalyptic number.

21552318 is an abundant number, since it is smaller than the sum of its proper divisors (26741202).

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

21552318 is a wasteful number, since it uses less digits than its factorization.

21552318 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133053 (or 133044 counting only the distinct ones).

The product of its digits is 2400, while the sum is 27.

The square root of 21552318 is about 4642.4474148880. The cubic root of 21552318 is about 278.2902528931.

The spelling of 21552318 in words is "twenty-one million, five hundred fifty-two thousand, three hundred eighteen".