21643786515 has 32 divisors (see below), whose sum is σ = 37312269120. Its totient is φ = 10650157056.

The previous prime is 21643786477. The next prime is 21643786517. The reversal of 21643786515 is 51568734612.

It is not a de Polignac number, because 21643786515 - 2¹⁰ = 21643785491 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21643786517) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 385771 + ... + 438299.

It is an arithmetic number, because the mean of its divisors is an integer number (1166008410).

Almost surely, 2^21643786515 is an apocalyptic number.

21643786515 is a deficient number, since it is larger than the sum of its proper divisors (15668482605).

21643786515 is a wasteful number, since it uses less digits than its factorization.

21643786515 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54663.

The product of its digits is 1209600, while the sum is 48.

The spelling of 21643786515 in words is "twenty-one billion, six hundred forty-three million, seven hundred eighty-six thousand, five hundred fifteen".