21378673440 has 144 divisors (see below), whose sum is σ = 75656887488. Its totient is φ = 5700969216.

The previous prime is 21378673427. The next prime is 21378673447. The reversal of 21378673440 is 4437687312.

21378673440 is a `hidden beast` number, since 2 + 137 + 8 + 6 + 73 + 440 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a super-2 number, since 2×21378673440² (a number of 21 digits) contains 22 as substring.

It is a hoax number, since the sum of its digits (45) coincides with the sum of the digits of its distinct prime factors.

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 (21378673447) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 236052 + ... + 313811.

It is an arithmetic number, because the mean of its divisors is an integer number (525395052).

Almost surely, 2^21378673440 is an apocalyptic number.

21378673440 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21378673440 is an abundant number, since it is smaller than the sum of its proper divisors (54278214048).

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

21378673440 is an equidigital number, since it uses as much as digits as its factorization.

21378673440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 549893 (or 549873 counting only the distinct ones).

The product of its (nonzero) digits is 677376, while the sum is 45.

The spelling of 21378673440 in words is "twenty-one billion, three hundred seventy-eight million, six hundred seventy-three thousand, four hundred forty".