20551440 has 160 divisors (see below), whose sum is σ = 78494976. Its totient is φ = 4331520.

The previous prime is 20551417. The next prime is 20551441. The reversal of 20551440 is 4415502.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (20551441) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 21370 + ... + 22310.

Almost surely, 2^20551440 is an apocalyptic number.

20551440 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 20551440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39247488).

20551440 is an abundant number, since it is smaller than the sum of its proper divisors (57943536).

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

20551440 is a wasteful number, since it uses less digits than its factorization.

20551440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 977 (or 971 counting only the distinct ones).

The product of its (nonzero) digits is 800, while the sum is 21.

The square root of 20551440 is about 4533.3696076980. The cubic root of 20551440 is about 273.9139090533.

Adding to 20551440 its reverse (4415502), we get a palindrome (24966942).

The spelling of 20551440 in words is "twenty million, five hundred fifty-one thousand, four hundred forty".