21505776890 has 16 divisors (see below), whose sum is σ = 41688121608. Its totient is φ = 7940594496.

The previous prime is 21505776857. The next prime is 21505776893. The reversal of 21505776890 is 9867750512.

It can be written as a sum of positive squares in 4 ways, for example, as 7649426521 + 13856350369 = 87461^2 + 117713^2 .

It is not an unprimeable number, because it can be changed into a prime (21505776893) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 82714397 + ... + 82714656.

Almost surely, 2^21505776890 is an apocalyptic number.

21505776890 is a deficient number, since it is larger than the sum of its proper divisors (20182344718).

21505776890 is a wasteful number, since it uses less digits than its factorization.

21505776890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 165429073.

The product of its (nonzero) digits is 1058400, while the sum is 50.

The spelling of 21505776890 in words is "twenty-one billion, five hundred five million, seven hundred seventy-six thousand, eight hundred ninety".