21398178852 has 18 divisors (see below), whose sum is σ = 54089841078. Its totient is φ = 7132726272.

The previous prime is 21398178787. The next prime is 21398178853. The reversal of 21398178852 is 25887189312.

21398178852 is a `hidden beast` number, since 2 + 1 + 398 + 178 + 85 + 2 = 666.

It can be written as a sum of positive squares in only one way, i.e., 15164444736 + 6233734116 = 123144^2 + 78954^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21398178853) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 297196893 + ... + 297196964.

It is an arithmetic number, because the mean of its divisors is an integer number (3004991171).

Almost surely, 2^21398178852 is an apocalyptic number.

It is an amenable number.

21398178852 is an abundant number, since it is smaller than the sum of its proper divisors (32691662226).

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

21398178852 is a wasteful number, since it uses less digits than its factorization.

21398178852 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 594393867 (or 594393862 counting only the distinct ones).

The product of its digits is 1935360, while the sum is 54.

The spelling of 21398178852 in words is "twenty-one billion, three hundred ninety-eight million, one hundred seventy-eight thousand, eight hundred fifty-two".