21538945390 has 16 divisors (see below), whose sum is σ = 40020750720. Its totient is φ = 8337656160.

The previous prime is 21538945369. The next prime is 21538945391. The reversal of 21538945390 is 9354983512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538945391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 34739925 + ... + 34740544.

It is an arithmetic number, because the mean of its divisors is an integer number (2501296920).

Almost surely, 2^21538945390 is an apocalyptic number.

21538945390 is a deficient number, since it is larger than the sum of its proper divisors (18481805330).

21538945390 is a wasteful number, since it uses less digits than its factorization.

21538945390 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69480507.

The product of its (nonzero) digits is 1166400, while the sum is 49.

The spelling of 21538945390 in words is "twenty-one billion, five hundred thirty-eight million, nine hundred forty-five thousand, three hundred ninety".