21553532 has 72 divisors (see below), whose sum is σ = 51614640. Its totient is φ = 7741440.

The previous prime is 21553531. The next prime is 21553613. The reversal of 21553532 is 23535512.

It is a super-3 number, since 3×21553532³ (a number of 23 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (26).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21553531) 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, 27644 + ... + 28412.

It is an arithmetic number, because the mean of its divisors is an integer number (716870).

Almost surely, 2^21553532 is an apocalyptic number.

21553532 is a gapful number since it is divisible by the number (22) 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 21553532, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25807320).

21553532 is an abundant number, since it is smaller than the sum of its proper divisors (30061108).

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

21553532 is a wasteful number, since it uses less digits than its factorization.

21553532 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 811 (or 802 counting only the distinct ones).

The product of its digits is 4500, while the sum is 26.

The square root of 21553532 is about 4642.5781630469. The cubic root of 21553532 is about 278.2954779772.

The spelling of 21553532 in words is "twenty-one million, five hundred fifty-three thousand, five hundred thirty-two".