21720717575 has 12 divisors (see below), whose sum is σ = 28104720528. Its totient is φ = 16621070400.

The previous prime is 21720717563. The next prime is 21720717649. The reversal of 21720717575 is 57571702712.

It is not a de Polignac number, because 21720717575 - 2¹⁰ = 21720716551 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 18887006 + ... + 18888155.

It is an arithmetic number, because the mean of its divisors is an integer number (2342060044).

Almost surely, 2^21720717575 is an apocalyptic number.

21720717575 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21720717575 is a deficient number, since it is larger than the sum of its proper divisors (6384002953).

21720717575 is a wasteful number, since it uses less digits than its factorization.

21720717575 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37775194 (or 37775189 counting only the distinct ones).

The product of its (nonzero) digits is 240100, while the sum is 44.

The spelling of 21720717575 in words is "twenty-one billion, seven hundred twenty million, seven hundred seventeen thousand, five hundred seventy-five".