21518409699 has 10 divisors (see below), whose sum is σ = 32144784980. Its totient is φ = 14345606412.

The previous prime is 21518409691. The next prime is 21518409763. The reversal of 21518409699 is 99690481512.

21518409699 is a `hidden beast` number, since 21 + 518 + 40 + 9 + 69 + 9 = 666.

It is not a de Polignac number, because 21518409699 - 2³ = 21518409691 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21518409691) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 132829609 + ... + 132829770.

It is an arithmetic number, because the mean of its divisors is an integer number (3214478498).

Almost surely, 2^21518409699 is an apocalyptic number.

21518409699 is a deficient number, since it is larger than the sum of its proper divisors (10626375281).

21518409699 is an equidigital number, since it uses as much as digits as its factorization.

21518409699 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265659391 (or 265659382 counting only the distinct ones).

The product of its (nonzero) digits is 1399680, while the sum is 54.

The spelling of 21518409699 in words is "twenty-one billion, five hundred eighteen million, four hundred nine thousand, six hundred ninety-nine".