21236614661 has 2 divisors, whose sum is σ = 21236614662. Its totient is φ = 21236614660.

The previous prime is 21236614631. The next prime is 21236614691. The reversal of 21236614661 is 16641663212.

It is a balanced prime because it is at equal distance from previous prime (21236614631) and next prime (21236614691).

It can be written as a sum of positive squares in only one way, i.e., 17695650625 + 3540964036 = 133025^2 + 59506^2 .

It is a cyclic number.

It is not a de Polignac number, because 21236614661 - 2¹⁰ = 21236613637 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21236614631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10618307330 + 10618307331.

It is an arithmetic number, because the mean of its divisors is an integer number (10618307331).

Almost surely, 2^21236614661 is an apocalyptic number.

It is an amenable number.

21236614661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21236614661 is an equidigital number, since it uses as much as digits as its factorization.

21236614661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 62208, while the sum is 38.

The spelling of 21236614661 in words is "twenty-one billion, two hundred thirty-six million, six hundred fourteen thousand, six hundred sixty-one".