21102012020 has 24 divisors (see below), whose sum is σ = 45395061768. Its totient is φ = 8234931200.

The previous prime is 21102011999. The next prime is 21102012031. The reversal of 21102012020 is 2021020112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 717596944 + 20384415076 = 26788^2 + 142774^2 .

It is a super-2 number, since 2×21102012020² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21102011992 and 21102012010.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12866261 + ... + 12867900.

It is an arithmetic number, because the mean of its divisors is an integer number (1891460907).

Almost surely, 2^21102012020 is an apocalyptic number.

21102012020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21102012020 is an abundant number, since it is smaller than the sum of its proper divisors (24293049748).

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

21102012020 is a wasteful number, since it uses less digits than its factorization.

21102012020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25734211 (or 25734209 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21102012020 its reverse (2021020112), we get a palindrome (23123032132).

The spelling of 21102012020 in words is "twenty-one billion, one hundred two million, twelve thousand, twenty".