21355506 has 48 divisors (see below), whose sum is σ = 49926240. Its totient is φ = 6575040.

The previous prime is 21355501. The next prime is 21355507. The reversal of 21355506 is 60555312.

It is a self number, because there is not a number n which added to its sum of digits gives 21355506.

It is not an unprimeable number, because it can be changed into a prime (21355501) 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, 13261 + ... + 14783.

It is an arithmetic number, because the mean of its divisors is an integer number (1040130).

Almost surely, 2^21355506 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21355506, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24963120).

21355506 is an abundant number, since it is smaller than the sum of its proper divisors (28570734).

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

21355506 is a wasteful number, since it uses less digits than its factorization.

21355506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1591 (or 1588 counting only the distinct ones).

The product of its (nonzero) digits is 4500, while the sum is 27.

The square root of 21355506 is about 4621.2017917421. The cubic root of 21355506 is about 277.4405618985.

The spelling of 21355506 in words is "twenty-one million, three hundred fifty-five thousand, five hundred six".