21388402116 has 18 divisors (see below), whose sum is σ = 54065127662. Its totient is φ = 7129467360.

The previous prime is 21388402111. The next prime is 21388402129. The reversal of 21388402116 is 61120488312.

21388402116 is a `hidden beast` number, since 2 + 138 + 8 + 402 + 116 = 666.

It can be written as a sum of positive squares in only one way, i.e., 16577592516 + 4810809600 = 128754^2 + 69360^2 .

It is a tau number, because it is divible by the number of its divisors (18).

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 594122281 = 21388402116 / (2 + 1 + 3 + 8 + 8 + 4 + 0 + 2 + 1 + 1 + 6).

It is not an unprimeable number, because it can be changed into a prime (21388402111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 297061105 + ... + 297061176.

Almost surely, 2^21388402116 is an apocalyptic number.

It is an amenable number.

21388402116 is an abundant number, since it is smaller than the sum of its proper divisors (32676725546).

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

21388402116 is a wasteful number, since it uses less digits than its factorization.

21388402116 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 594122291 (or 594122286 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The spelling of 21388402116 in words is "twenty-one billion, three hundred eighty-eight million, four hundred two thousand, one hundred sixteen".