21000120256 has 14 divisors (see below), whose sum is σ = 41672113760. Its totient is φ = 10500060096.

The previous prime is 21000120221. The next prime is 21000120257. The reversal of 21000120256 is 65202100012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000120257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 164063376 + ... + 164063503.

Almost surely, 2^21000120256 is an apocalyptic number.

It is an amenable number.

21000120256 is a deficient number, since it is larger than the sum of its proper divisors (20671993504).

21000120256 is an equidigital number, since it uses as much as digits as its factorization.

21000120256 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328126891 (or 328126881 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 19.

Adding to 21000120256 its reverse (65202100012), we get a palindrome (86202220268).

The spelling of 21000120256 in words is "twenty-one billion, one hundred twenty thousand, two hundred fifty-six".