21551040 has 168 divisors, whose sum is σ = 84795360. Its totient is φ = 4921344.

The previous prime is 21551039. The next prime is 21551071. The reversal of 21551040 is 4015512.

It is a tau number, because it is divible by the number of its divisors (168).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 19626 + ... + 20694.

Almost surely, 2^21551040 is an apocalyptic number.

21551040 is a gapful number since it is divisible by the number (20) 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 21551040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42397680).

21551040 is an abundant number, since it is smaller than the sum of its proper divisors (63244320).

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

21551040 is a wasteful number, since it uses less digits than its factorization.

21551040 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1099 (or 1086 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21551040 is about 4642.3097699313. The cubic root of 21551040 is about 278.2847521395.

Adding to 21551040 its reverse (4015512), we get a palindrome (25566552).

The spelling of 21551040 in words is "twenty-one million, five hundred fifty-one thousand, forty".