21406774640 has 20 divisors (see below), whose sum is σ = 49770751224. Its totient is φ = 8562709824.

The previous prime is 21406774639. The next prime is 21406774661. The reversal of 21406774640 is 4647760412.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 133792262 + ... + 133792421.

Almost surely, 2^21406774640 is an apocalyptic number.

21406774640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21406774640 is an abundant number, since it is smaller than the sum of its proper divisors (28363976584).

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

21406774640 is a wasteful number, since it uses less digits than its factorization.

21406774640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 267584696 (or 267584690 counting only the distinct ones).

The product of its (nonzero) digits is 225792, while the sum is 41.

The spelling of 21406774640 in words is "twenty-one billion, four hundred six million, seven hundred seventy-four thousand, six hundred forty".