21123000000 has 294 divisors, whose sum is σ = 75712858988. Its totient is φ = 5630400000.

The previous prime is 21122999983. The next prime is 21123000001. The reversal of 21123000000 is 32112.

It is a happy number.

It is a super-2 number, since 2×21123000000² (a number of 21 digits) contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21123000001) by changing a digit.

It is a polite number, since it can be written in 41 ways as a sum of consecutive naturals, for example, 8998827 + ... + 9001173.

Almost surely, 2^21123000000 is an apocalyptic number.

21123000000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21123000000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37856429494).

21123000000 is an abundant number, since it is smaller than the sum of its proper divisors (54589858988).

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

21123000000 is an frugal number, since it uses more digits than its factorization.

21123000000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2395 (or 2357 counting only the distinct ones).

The product of its (nonzero) digits is 12, while the sum is 9.

Adding to 21123000000 its reverse (32112), we get a palindrome (21123032112).

The spelling of 21123000000 in words is "twenty-one billion, one hundred twenty-three million", and thus it is an aban number.