21010012020 has 72 divisors (see below), whose sum is σ = 67479224904. Its totient is φ = 5273100288.

The previous prime is 21010012019. The next prime is 21010012027. The reversal of 21010012020 is 2021001012.

It can be written as a sum of positive squares in 4 ways, for example, as 7978419684 + 13031592336 = 89322^2 + 114156^2 .

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21010011993 and 21010012011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010012027) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3429949 + ... + 3436068.

It is an arithmetic number, because the mean of its divisors is an integer number (937211457).

Almost surely, 2^21010012020 is an apocalyptic number.

21010012020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21010012020 is an abundant number, since it is smaller than the sum of its proper divisors (46469212884).

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

21010012020 is a wasteful number, since it uses less digits than its factorization.

21010012020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6866049 (or 6866044 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21010012020 its reverse (2021001012), we get a palindrome (23031013032).

The spelling of 21010012020 in words is "twenty-one billion, ten million, twelve thousand, twenty".