21386818440 has 384 divisors, whose sum is σ = 77628227040. Its totient is φ = 5072191488.

The previous prime is 21386818429. The next prime is 21386818447. The reversal of 21386818440 is 4481868312.

21386818440 is a `hidden beast` number, since 2 + 138 + 68 + 18 + 440 = 666.

It can be written as a sum of positive squares in 16 ways, for example, as 2654516484 + 18732301956 = 51522^2 + 136866^2 .

It is a Harshad number since it is a multiple of its sum of digits (45).

It is not an unprimeable number, because it can be changed into a prime (21386818447) 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 95 ways as a sum of consecutive naturals, for example, 19566534 + ... + 19567626.

Almost surely, 2^21386818440 is an apocalyptic number.

21386818440 is a gapful number since it is divisible by the number (20) 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 21386818440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38814113520).

21386818440 is an abundant number, since it is smaller than the sum of its proper divisors (56241408600).

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

21386818440 is a wasteful number, since it uses less digits than its factorization.

21386818440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1273 (or 1266 counting only the distinct ones).

The product of its (nonzero) digits is 294912, while the sum is 45.

The spelling of 21386818440 in words is "twenty-one billion, three hundred eighty-six million, eight hundred eighteen thousand, four hundred forty".