21540385394 has 24 divisors (see below), whose sum is σ = 35522977980. Its totient is φ = 9788866560.

The previous prime is 21540385357. The next prime is 21540385403. The reversal of 21540385394 is 49358304512.

It can be written as a sum of positive squares in 2 ways, for example, as 21137379769 + 403005625 = 145387^2 + 20075^2 .

It is a Smith number, since the sum of its digits (44) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1573202 + ... + 1586834.

Almost surely, 2^21540385394 is an apocalyptic number.

21540385394 is a deficient number, since it is larger than the sum of its proper divisors (13982592586).

21540385394 is a wasteful number, since it uses less digits than its factorization.

21540385394 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20186 (or 20175 counting only the distinct ones).

The product of its (nonzero) digits is 518400, while the sum is 44.

The spelling of 21540385394 in words is "twenty-one billion, five hundred forty million, three hundred eighty-five thousand, three hundred ninety-four".