21256973653728 has 48 divisors (see below), whose sum is σ = 55799897037696. Its totient is φ = 7085614558080.

The previous prime is 21256973653711. The next prime is 21256973653757. The reversal of 21256973653728 is 82735637965212.

It is a tau number, because it is divible by the number of its divisors (48).

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, 17685333 + ... + 18849003.

It is an arithmetic number, because the mean of its divisors is an integer number (1162497854952).

Almost surely, 2^{21256973653728} is an apocalyptic number.

It is an amenable number.

21256973653728 is an abundant number, since it is smaller than the sum of its proper divisors (34542923383968).

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

21256973653728 is a wasteful number, since it uses less digits than its factorization.

21256973653728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1353967 (or 1353959 counting only the distinct ones).

The product of its digits is 228614400, while the sum is 66.

The spelling of 21256973653728 in words is "twenty-one trillion, two hundred fifty-six billion, nine hundred seventy-three million, six hundred fifty-three thousand, seven hundred twenty-eight".