21864635669 has 2 divisors, whose sum is σ = 21864635670. Its totient is φ = 21864635668.

The previous prime is 21864635651. The next prime is 21864635671. The reversal of 21864635669 is 96653646812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20476179025 + 1388456644 = 143095^2 + 37262^2 .

It is a cyclic number.

It is not a de Polignac number, because 21864635669 - 2³² = 17569668373 is a prime.

It is a super-2 number, since 2×21864635669² (a number of 21 digits) contains 22 as substring.

Together with 21864635671, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21864635269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932317834 + 10932317835.

It is an arithmetic number, because the mean of its divisors is an integer number (10932317835).

Almost surely, 2^21864635669 is an apocalyptic number.

It is an amenable number.

21864635669 is a deficient number, since it is larger than the sum of its proper divisors (1).

21864635669 is an equidigital number, since it uses as much as digits as its factorization.

21864635669 is an evil number, because the sum of its binary digits is even.

The product of its digits is 11197440, while the sum is 56.

The spelling of 21864635669 in words is "twenty-one billion, eight hundred sixty-four million, six hundred thirty-five thousand, six hundred sixty-nine".