21644343377 has 4 divisors (see below), whose sum is σ = 21651558756. Its totient is φ = 21637128000.

The previous prime is 21644343323. The next prime is 21644343451. The reversal of 21644343377 is 77334344612.

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 5464757776 + 16179585601 = 73924^2 + 127199^2 .

It is a cyclic number.

It is not a de Polignac number, because 21644343377 - 2¹⁴ = 21644326993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21644343277) 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, 3603188 + ... + 3609189.

It is an arithmetic number, because the mean of its divisors is an integer number (5412889689).

Almost surely, 2^21644343377 is an apocalyptic number.

It is an amenable number.

21644343377 is a deficient number, since it is larger than the sum of its proper divisors (7215379).

21644343377 is an equidigital number, since it uses as much as digits as its factorization.

21644343377 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7215378.

The product of its digits is 1016064, while the sum is 44.

Adding to 21644343377 its reverse (77334344612), we get a palindrome (98978687989).

The spelling of 21644343377 in words is "twenty-one billion, six hundred forty-four million, three hundred forty-three thousand, three hundred seventy-seven".