21784408688 has 20 divisors (see below), whose sum is σ = 48236905200. Its totient is φ = 9336175104.

The previous prime is 21784408649. The next prime is 21784408757. The reversal of 21784408688 is 88680448712.

It is a Smith number, since the sum of its digits (56) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (56).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 97251713 + ... + 97251936.

It is an arithmetic number, because the mean of its divisors is an integer number (2411845260).

Almost surely, 2^21784408688 is an apocalyptic number.

21784408688 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21784408688 is an abundant number, since it is smaller than the sum of its proper divisors (26452496512).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21784408688 is a wasteful number, since it uses less digits than its factorization.

21784408688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 194503664 (or 194503658 counting only the distinct ones).

The product of its (nonzero) digits is 5505024, while the sum is 56.

The spelling of 21784408688 in words is "twenty-one billion, seven hundred eighty-four million, four hundred eight thousand, six hundred eighty-eight".