21728690784 has 36 divisors (see below), whose sum is σ = 61790965236. Its totient is φ = 7242896832.

The previous prime is 21728690773. The next prime is 21728690891. The reversal of 21728690784 is 48709682712.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (36).

It is a self number, because there is not a number n which added to its sum of digits gives 21728690784.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 37723134 + ... + 37723709.

It is an arithmetic number, because the mean of its divisors is an integer number (1716415701).

Almost surely, 2^21728690784 is an apocalyptic number.

21728690784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21728690784 is an abundant number, since it is smaller than the sum of its proper divisors (40062274452).

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

21728690784 is a wasteful number, since it uses less digits than its factorization.

21728690784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75446859 (or 75446848 counting only the distinct ones).

The product of its (nonzero) digits is 2709504, while the sum is 54.

The spelling of 21728690784 in words is "twenty-one billion, seven hundred twenty-eight million, six hundred ninety thousand, seven hundred eighty-four".