21378434405 has 24 divisors (see below), whose sum is σ = 27407088072. Its totient is φ = 15953444864.

The previous prime is 21378434401. The next prime is 21378434419. The reversal of 21378434405 is 50443487312.

It can be written as a sum of positive squares in 12 ways, for example, as 18175893124 + 3202541281 = 134818^2 + 56591^2 .

It is not a de Polignac number, because 21378434405 - 2² = 21378434401 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21378434401) 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, 1075517 + ... + 1095213.

It is an arithmetic number, because the mean of its divisors is an integer number (1141962003).

Almost surely, 2^21378434405 is an apocalyptic number.

It is an amenable number.

21378434405 is a deficient number, since it is larger than the sum of its proper divisors (6028653667).

21378434405 is a wasteful number, since it uses less digits than its factorization.

21378434405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19945 (or 19832 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 41.

The spelling of 21378434405 in words is "twenty-one billion, three hundred seventy-eight million, four hundred thirty-four thousand, four hundred five".