21209845615 has 16 divisors (see below), whose sum is σ = 29182551552. Its totient is φ = 14496512544.

The previous prime is 21209845603. The next prime is 21209845733. The reversal of 21209845615 is 51654890212.

It is a cyclic number.

It is not a de Polignac number, because 21209845615 - 2¹³ = 21209837423 is a prime.

It is a congruent number.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 976219 + ... + 997708.

It is an arithmetic number, because the mean of its divisors is an integer number (1823909472).

Almost surely, 2^21209845615 is an apocalyptic number.

21209845615 is a deficient number, since it is larger than the sum of its proper divisors (7972705937).

21209845615 is a wasteful number, since it uses less digits than its factorization.

21209845615 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1974246.

The product of its (nonzero) digits is 172800, while the sum is 43.

The spelling of 21209845615 in words is "twenty-one billion, two hundred nine million, eight hundred forty-five thousand, six hundred fifteen".