21381552243 has 18 divisors (see below), whose sum is σ = 31606959956. Its totient is φ = 13920998112.

The previous prime is 21381552211. The next prime is 21381552251. The reversal of 21381552243 is 34225518312.

21381552243 is a `hidden beast` number, since 2 + 1 + 3 + 81 + 552 + 24 + 3 = 666.

It is not a de Polignac number, because 21381552243 - 2⁵ = 21381552211 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21381552198 and 21381552207.

It is not an unprimeable number, because it can be changed into a prime (21381552253) by changing a digit.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 2872855 + ... + 2880287.

Almost surely, 2^21381552243 is an apocalyptic number.

21381552243 is a deficient number, since it is larger than the sum of its proper divisors (10225407713).

21381552243 is an frugal number, since it uses more digits than its factorization.

21381552243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14915 (or 7479 counting only the distinct ones).

The product of its digits is 57600, while the sum is 36.

The spelling of 21381552243 in words is "twenty-one billion, three hundred eighty-one million, five hundred fifty-two thousand, two hundred forty-three".