21012220423 has 4 divisors (see below), whose sum is σ = 21925795248. Its totient is φ = 20098645600.

The previous prime is 21012220381. The next prime is 21012220429. The reversal of 21012220423 is 32402221012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21012220423 - 2¹³ = 21012212231 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21012220423.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012220429) 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, 456787378 + ... + 456787423.

It is an arithmetic number, because the mean of its divisors is an integer number (5481448812).

Almost surely, 2^21012220423 is an apocalyptic number.

21012220423 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21012220423 is a deficient number, since it is larger than the sum of its proper divisors (913574825).

21012220423 is an equidigital number, since it uses as much as digits as its factorization.

21012220423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 913574824.

The product of its (nonzero) digits is 384, while the sum is 19.

Adding to 21012220423 its reverse (32402221012), we get a palindrome (53414441435).

The spelling of 21012220423 in words is "twenty-one billion, twelve million, two hundred twenty thousand, four hundred twenty-three".