21000646318 has 4 divisors (see below), whose sum is σ = 31500969480. Its totient is φ = 10500323158.

The previous prime is 21000646313. The next prime is 21000646319. The reversal of 21000646318 is 81364600012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21000646318.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000646313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5250161578 + ... + 5250161581.

It is an arithmetic number, because the mean of its divisors is an integer number (7875242370).

Almost surely, 2^21000646318 is an apocalyptic number.

21000646318 is a deficient number, since it is larger than the sum of its proper divisors (10500323162).

21000646318 is a wasteful number, since it uses less digits than its factorization.

21000646318 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10500323161.

The product of its (nonzero) digits is 6912, while the sum is 31.

The spelling of 21000646318 in words is "twenty-one billion, six hundred forty-six thousand, three hundred eighteen".