21254061808 has 80 divisors (see below), whose sum is σ = 49574763520. Its totient is φ = 8623335168.

The previous prime is 21254061797. The next prime is 21254061809. The reversal of 21254061808 is 80816045212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21254061809) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4110841 + ... + 4116007.

It is an arithmetic number, because the mean of its divisors is an integer number (619684544).

Almost surely, 2^21254061808 is an apocalyptic number.

21254061808 is a gapful number since it is divisible by the number (28) 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 21254061808, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24787381760).

21254061808 is an abundant number, since it is smaller than the sum of its proper divisors (28320701712).

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

21254061808 is a wasteful number, since it uses less digits than its factorization.

21254061808 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7134 (or 7128 counting only the distinct ones).

The product of its (nonzero) digits is 30720, while the sum is 37.

The spelling of 21254061808 in words is "twenty-one billion, two hundred fifty-four million, sixty-one thousand, eight hundred eight".