21506878436 has 12 divisors (see below), whose sum is σ = 37665842928. Its totient is φ = 10745209032.

The previous prime is 21506878363. The next prime is 21506878447. The reversal of 21506878436 is 63487860512.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2051666 + ... + 2062121.

It is an arithmetic number, because the mean of its divisors is an integer number (3138820244).

Almost surely, 2^21506878436 is an apocalyptic number.

It is an amenable number.

21506878436 is a deficient number, since it is larger than the sum of its proper divisors (16158964492).

21506878436 is a wasteful number, since it uses less digits than its factorization.

21506878436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4115098 (or 4115096 counting only the distinct ones).

The product of its (nonzero) digits is 1935360, while the sum is 50.

The spelling of 21506878436 in words is "twenty-one billion, five hundred six million, eight hundred seventy-eight thousand, four hundred thirty-six".