21665501423 has 2 divisors, whose sum is σ = 21665501424. Its totient is φ = 21665501422.

The previous prime is 21665501419. The next prime is 21665501461. The reversal of 21665501423 is 32410556612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21665501423 - 2² = 21665501419 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21665501483) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10832750711 + 10832750712.

It is an arithmetic number, because the mean of its divisors is an integer number (10832750712).

Almost surely, 2^21665501423 is an apocalyptic number.

21665501423 is a deficient number, since it is larger than the sum of its proper divisors (1).

21665501423 is an equidigital number, since it uses as much as digits as its factorization.

21665501423 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 43200, while the sum is 35.

The spelling of 21665501423 in words is "twenty-one billion, six hundred sixty-five million, five hundred one thousand, four hundred twenty-three".