21756023077 has 4 divisors (see below), whose sum is σ = 21756873600. Its totient is φ = 21755172556.

The previous prime is 21756023057. The next prime is 21756023083. The reversal of 21756023077 is 77032065712.

It is a happy number.

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 not a de Polignac number, because 21756023077 - 2⁷ = 21756022949 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 (21756023057) 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, 385663 + ... + 438460.

It is an arithmetic number, because the mean of its divisors is an integer number (5439218400).

Almost surely, 2^21756023077 is an apocalyptic number.

It is an amenable number.

21756023077 is a deficient number, since it is larger than the sum of its proper divisors (850523).

21756023077 is an equidigital number, since it uses as much as digits as its factorization.

21756023077 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 850522.

The product of its (nonzero) digits is 123480, while the sum is 40.

Adding to 21756023077 its reverse (77032065712), we get a palindrome (98788088789).

The spelling of 21756023077 in words is "twenty-one billion, seven hundred fifty-six million, twenty-three thousand, seventy-seven".