21420721773 has 48 divisors (see below), whose sum is σ = 34161701184. Its totient is φ = 12826356480.

The previous prime is 21420721759. The next prime is 21420721781. The reversal of 21420721773 is 37712702412.

It is not a de Polignac number, because 21420721773 - 2⁴ = 21420721757 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21420721703) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 2787865 + ... + 2795537.

It is an arithmetic number, because the mean of its divisors is an integer number (711702108).

Almost surely, 2^21420721773 is an apocalyptic number.

It is an amenable number.

21420721773 is a deficient number, since it is larger than the sum of its proper divisors (12740979411).

21420721773 is a wasteful number, since it uses less digits than its factorization.

21420721773 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8026 (or 8023 counting only the distinct ones).

The product of its (nonzero) digits is 32928, while the sum is 36.

The spelling of 21420721773 in words is "twenty-one billion, four hundred twenty million, seven hundred twenty-one thousand, seven hundred seventy-three".