21312020 has 12 divisors (see below), whose sum is σ = 44755284. Its totient is φ = 8524800.

The previous prime is 21312019. The next prime is 21312023. The reversal of 21312020 is 2021312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12082576 + 9229444 = 3476^2 + 3038^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21311992 and 21312010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312023) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 532781 + ... + 532820.

It is an arithmetic number, because the mean of its divisors is an integer number (3729607).

Almost surely, 2^21312020 is an apocalyptic number.

21312020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21312020 is an abundant number, since it is smaller than the sum of its proper divisors (23443264).

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

21312020 is a wasteful number, since it uses less digits than its factorization.

21312020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1065610 (or 1065608 counting only the distinct ones).

The product of its (nonzero) digits is 24, while the sum is 11.

The square root of 21312020 is about 4616.4943409475. The cubic root of 21312020 is about 277.2521174651.

Adding to 21312020 its reverse (2021312), we get a palindrome (23333332).

The spelling of 21312020 in words is "twenty-one million, three hundred twelve thousand, twenty".