21123423220 has 24 divisors (see below), whose sum is σ = 44652964608. Its totient is φ = 8393412000.

The previous prime is 21123423199. The next prime is 21123423271. The reversal of 21123423220 is 2232432112.

It is a junction number, because it is equal to n+sod(n) for n = 21123423191 and 21123423200.

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, 3494236 + ... + 3500275.

It is an arithmetic number, because the mean of its divisors is an integer number (1860540192).

Almost surely, 2^21123423220 is an apocalyptic number.

21123423220 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21123423220 is an abundant number, since it is smaller than the sum of its proper divisors (23529541388).

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

21123423220 is a wasteful number, since it uses less digits than its factorization.

21123423220 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6994671 (or 6994669 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 22.

Adding to 21123423220 its reverse (2232432112), we get a palindrome (23355855332).

The spelling of 21123423220 in words is "twenty-one billion, one hundred twenty-three million, four hundred twenty-three thousand, two hundred twenty".