21057720550 has 24 divisors (see below), whose sum is σ = 39172421376. Its totient is φ = 8421999840.

The previous prime is 21057720511. The next prime is 21057720569. The reversal of 21057720550 is 5502775012.

It is a congruent number.

It is an unprimeable number.

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 in 11 ways as a sum of consecutive naturals, for example, 444612 + ... + 489688.

It is an arithmetic number, because the mean of its divisors is an integer number (1632184224).

Almost surely, 2^21057720550 is an apocalyptic number.

21057720550 is a deficient number, since it is larger than the sum of its proper divisors (18114700826).

21057720550 is a wasteful number, since it uses less digits than its factorization.

21057720550 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54432 (or 54427 counting only the distinct ones).

The product of its (nonzero) digits is 24500, while the sum is 34.

The spelling of 21057720550 in words is "twenty-one billion, fifty-seven million, seven hundred twenty thousand, five hundred fifty".