21420265640 has 16 divisors (see below), whose sum is σ = 48195597780. Its totient is φ = 8568106240.

The previous prime is 21420265597. The next prime is 21420265673. The reversal of 21420265640 is 4656202412.

It can be written as a sum of positive squares in 2 ways, for example, as 20936353636 + 483912004 = 144694^2 + 21998^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21420265597 and 21420265606.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 267753281 + ... + 267753360.

Almost surely, 2^21420265640 is an apocalyptic number.

21420265640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21420265640 is an abundant number, since it is smaller than the sum of its proper divisors (26775332140).

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

21420265640 is a wasteful number, since it uses less digits than its factorization.

21420265640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 535506652 (or 535506648 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 32.

The spelling of 21420265640 in words is "twenty-one billion, four hundred twenty million, two hundred sixty-five thousand, six hundred forty".