21724520771 has 4 divisors (see below), whose sum is σ = 21968616600. Its totient is φ = 21480424944.

The previous prime is 21724520767. The next prime is 21724520777. The reversal of 21724520771 is 17702542712.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21724520771 - 2² = 21724520767 is a prime.

It is a super-2 number, since 2×21724520771² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21724520777) 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, 122047781 + ... + 122047958.

It is an arithmetic number, because the mean of its divisors is an integer number (5492154150).

Almost surely, 2^21724520771 is an apocalyptic number.

21724520771 is a deficient number, since it is larger than the sum of its proper divisors (244095829).

21724520771 is an equidigital number, since it uses as much as digits as its factorization.

21724520771 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244095828.

The product of its (nonzero) digits is 54880, while the sum is 38.

The spelling of 21724520771 in words is "twenty-one billion, seven hundred twenty-four million, five hundred twenty thousand, seven hundred seventy-one".