21581750712517 has 4 divisors (see below), whose sum is σ = 21600307679040. Its totient is φ = 21563193745996.

The previous prime is 21581750712449. The next prime is 21581750712527. The reversal of 21581750712517 is 71521705718512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21581750712517 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21581750712527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9278481517 + ... + 9278483842.

It is an arithmetic number, because the mean of its divisors is an integer number (5400076919760).

Almost surely, 2^{21581750712517} is an apocalyptic number.

It is an amenable number.

21581750712517 is a deficient number, since it is larger than the sum of its proper divisors (18556966523).

21581750712517 is a wasteful number, since it uses less digits than its factorization.

21581750712517 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18556966522.

The product of its (nonzero) digits is 1372000, while the sum is 52.

The spelling of 21581750712517 in words is "twenty-one trillion, five hundred eighty-one billion, seven hundred fifty million, seven hundred twelve thousand, five hundred seventeen".