21123121122020 has 24 divisors (see below), whose sum is σ = 45557434205304. Its totient is φ = 8220890382336.

The previous prime is 21123121121903. The next prime is 21123121122083. The reversal of 21123121122020 is 2022112132112.

It can be written as a sum of positive squares in 4 ways, for example, as 7042060001344 + 14081061120676 = 2653688^2 + 3752474^2 .

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a junction number, because it is equal to n+sod(n) for n = 21123121121983 and 21123121122001.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14272378397 + ... + 14272379876.

It is an arithmetic number, because the mean of its divisors is an integer number (1898226425221).

Almost surely, 2^{21123121122020} is an apocalyptic number.

21123121122020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21123121122020 is an abundant number, since it is smaller than the sum of its proper divisors (24434313083284).

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

21123121122020 is a wasteful number, since it uses less digits than its factorization.

21123121122020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28544758319 (or 28544758317 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 20.

Adding to 21123121122020 its reverse (2022112132112), we get a palindrome (23145233254132).

The spelling of 21123121122020 in words is "twenty-one trillion, one hundred twenty-three billion, one hundred twenty-one million, one hundred twenty-two thousand, twenty".