21641717644 has 24 divisors (see below), whose sum is σ = 39160775808. Its totient is φ = 10454104320.

The previous prime is 21641717563. The next prime is 21641717701. The reversal of 21641717644 is 44671714612.

It is a self number, because there is not a number n which added to its sum of digits gives 21641717644.

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 7 ways as a sum of consecutive naturals, for example, 73627 + ... + 220690.

It is an arithmetic number, because the mean of its divisors is an integer number (1631698992).

Almost surely, 2^21641717644 is an apocalyptic number.

It is an amenable number.

21641717644 is a deficient number, since it is larger than the sum of its proper divisors (17519058164).

21641717644 is a wasteful number, since it uses less digits than its factorization.

21641717644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 294945 (or 294943 counting only the distinct ones).

The product of its digits is 225792, while the sum is 43.

The spelling of 21641717644 in words is "twenty-one billion, six hundred forty-one million, seven hundred seventeen thousand, six hundred forty-four".