21018652478208 has 2160 divisors, whose sum is σ = 81729224881920. Its totient is φ = 5333116723200.

The previous prime is 21018652478147. The next prime is 21018652478209. The reversal of 21018652478208 is 80287425681012.

21018652478208 is a `hidden beast` number, since 2 + 10 + 1 + 86 + 524 + 7 + 8 + 20 + 8 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is not an unprimeable number, because it can be changed into a prime (21018652478209) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 239 ways as a sum of consecutive naturals, for example, 192831674058 + ... + 192831674166.

It is an arithmetic number, because the mean of its divisors is an integer number (37837604112).

Almost surely, 2^{21018652478208} is an apocalyptic number.

21018652478208 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21018652478208, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (40864612440960).

21018652478208 is an abundant number, since it is smaller than the sum of its proper divisors (60710572403712).

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

21018652478208 is an frugal number, since it uses more digits than its factorization.

21018652478208 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 248 (or 203 counting only the distinct ones).

The product of its (nonzero) digits is 3440640, while the sum is 54.

The spelling of 21018652478208 in words is "twenty-one trillion, eighteen billion, six hundred fifty-two million, four hundred seventy-eight thousand, two hundred eight".