21505766519 has 2 divisors, whose sum is σ = 21505766520. Its totient is φ = 21505766518.

The previous prime is 21505766467. The next prime is 21505766533. The reversal of 21505766519 is 91566750512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21505766519 - 2²⁰ = 21504717943 is a prime.

It is a super-2 number, since 2×21505766519² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21505766549) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752883259 + 10752883260.

It is an arithmetic number, because the mean of its divisors is an integer number (10752883260).

Almost surely, 2^21505766519 is an apocalyptic number.

21505766519 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505766519 is an equidigital number, since it uses as much as digits as its factorization.

21505766519 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 567000, while the sum is 47.

The spelling of 21505766519 in words is "twenty-one billion, five hundred five million, seven hundred sixty-six thousand, five hundred nineteen".