21255534 has 40 divisors (see below), whose sum is σ = 47959560. Its totient is φ = 7035984.

The previous prime is 21255529. The next prime is 21255541. The reversal of 21255534 is 43555212.

It is a happy number.

21255534 is a `hidden beast` number, since 2 + 125 + 5 + 534 = 666.

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

It is a Curzon number.

It is a plaindrome in base 16.

It is a junction number, because it is equal to n+sod(n) for n = 21255498 and 21255507.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 28632 + ... + 29364.

It is an arithmetic number, because the mean of its divisors is an integer number (1198989).

Almost surely, 2^21255534 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21255534, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23979780).

21255534 is an abundant number, since it is smaller than the sum of its proper divisors (26704026).

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

21255534 is a wasteful number, since it uses less digits than its factorization.

21255534 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 926 (or 917 counting only the distinct ones).

The product of its digits is 6000, while the sum is 27.

The square root of 21255534 is about 4610.3724361487. The cubic root of 21255534 is about 277.0069550400.

The spelling of 21255534 in words is "twenty-one million, two hundred fifty-five thousand, five hundred thirty-four".