21551020 has 24 divisors (see below), whose sum is σ = 46481904. Its totient is φ = 8387136.

The previous prime is 21550939. The next prime is 21551039. The reversal of 21551020 is 2015512.

It is a junction number, because it is equal to n+sod(n) for n = 21550985 and 21551003.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13822 + ... + 15301.

It is an arithmetic number, because the mean of its divisors is an integer number (1936746).

Almost surely, 2^21551020 is an apocalyptic number.

21551020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21551020 is an abundant number, since it is smaller than the sum of its proper divisors (24930884).

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

21551020 is a wasteful number, since it uses less digits than its factorization.

21551020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29169 (or 29167 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21551020 is about 4642.3076158307. The cubic root of 21551020 is about 278.2846660540.

Adding to 21551020 its reverse (2015512), we get a palindrome (23566532).

The spelling of 21551020 in words is "twenty-one million, five hundred fifty-one thousand, twenty".