21756704773 has 4 divisors (see below), whose sum is σ = 22001162220. Its totient is φ = 21512247328.

The previous prime is 21756704747. The next prime is 21756704789. The reversal of 21756704773 is 37740765712.

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

It can be written as a sum of positive squares in 2 ways, for example, as 11127507169 + 10629197604 = 105487^2 + 103098^2 .

It is a cyclic number.

It is not a de Polignac number, because 21756704773 - 2⁵ = 21756704741 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 (21756704743) 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, 122228590 + ... + 122228767.

It is an arithmetic number, because the mean of its divisors is an integer number (5500290555).

Almost surely, 2^21756704773 is an apocalyptic number.

It is an amenable number.

21756704773 is a deficient number, since it is larger than the sum of its proper divisors (244457447).

21756704773 is an equidigital number, since it uses as much as digits as its factorization.

21756704773 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244457446.

The product of its (nonzero) digits is 1728720, while the sum is 49.

The spelling of 21756704773 in words is "twenty-one billion, seven hundred fifty-six million, seven hundred four thousand, seven hundred seventy-three".