21200123256 has 32 divisors (see below), whose sum is σ = 57077255760. Its totient is φ = 6523114752.

The previous prime is 21200123239. The next prime is 21200123267. The reversal of 21200123256 is 65232100212.

It is a Harshad number since it is a multiple of its sum of digits (24).

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, 33974245 + ... + 33974868.

Almost surely, 2^21200123256 is an apocalyptic number.

21200123256 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

21200123256 is an abundant number, since it is smaller than the sum of its proper divisors (35877132504).

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

21200123256 is a wasteful number, since it uses less digits than its factorization.

21200123256 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67949135 (or 67949131 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

Adding to 21200123256 its reverse (65232100212), we get a palindrome (86432223468).

The spelling of 21200123256 in words is "twenty-one billion, two hundred million, one hundred twenty-three thousand, two hundred fifty-six".