21117717390 has 768 divisors, whose sum is σ = 74132029440. Its totient is φ = 3740774400.

The previous prime is 21117717349. The next prime is 21117717391. The reversal of 21117717390 is 9371771112.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21117717391) by changing a digit.

It is a polite number, since it can be written in 383 ways as a sum of consecutive naturals, for example, 254430289 + ... + 254430371.

It is an arithmetic number, because the mean of its divisors is an integer number (96526080).

Almost surely, 2^21117717390 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21117717390, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37066014720).

21117717390 is an abundant number, since it is smaller than the sum of its proper divisors (53014312050).

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

21117717390 is a wasteful number, since it uses less digits than its factorization.

21117717390 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189 (or 178 counting only the distinct ones).

The product of its (nonzero) digits is 18522, while the sum is 39.

The spelling of 21117717390 in words is "twenty-one billion, one hundred seventeen million, seven hundred seventeen thousand, three hundred ninety".