21311020 has 24 divisors (see below), whose sum is σ = 44877168. Its totient is φ = 8500800.

The previous prime is 21310999. The next prime is 21311033. The reversal of 21311020 is 2011312.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21310988 and 21311006.

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 7 ways as a sum of consecutive naturals, for example, 7155 + ... + 9685.

It is an arithmetic number, because the mean of its divisors is an integer number (1869882).

Almost surely, 2^21311020 is an apocalyptic number.

21311020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21311020 is an abundant number, since it is smaller than the sum of its proper divisors (23566148).

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

21311020 is a wasteful number, since it uses less digits than its factorization.

21311020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2961 (or 2959 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 10.

The square root of 21311020 is about 4616.3860323851. The cubic root of 21311020 is about 277.2477810006.

Adding to 21311020 its reverse (2011312), we get a palindrome (23322332).

The spelling of 21311020 in words is "twenty-one million, three hundred eleven thousand, twenty".