21684376628 has 6 divisors (see below), whose sum is σ = 37947659106. Its totient is φ = 10842188312.

The previous prime is 21684376627. The next prime is 21684376661. The reversal of 21684376628 is 82667348612.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20847894544 + 836482084 = 144388^2 + 28922^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21684376628.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21684376627) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2710547075 + ... + 2710547082.

It is an arithmetic number, because the mean of its divisors is an integer number (6324609851).

Almost surely, 2^21684376628 is an apocalyptic number.

It is an amenable number.

21684376628 is a deficient number, since it is larger than the sum of its proper divisors (16263282478).

21684376628 is a wasteful number, since it uses less digits than its factorization.

21684376628 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5421094161 (or 5421094159 counting only the distinct ones).

The product of its digits is 4644864, while the sum is 53.

The spelling of 21684376628 in words is "twenty-one billion, six hundred eighty-four million, three hundred seventy-six thousand, six hundred twenty-eight".