21043542434 has 4 divisors (see below), whose sum is σ = 31565313654. Its totient is φ = 10521771216.

The previous prime is 21043542427. The next prime is 21043542437. The reversal of 21043542434 is 43424534012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 19283488225 + 1760054209 = 138865^2 + 41953^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21043542434.

It is not an unprimeable number, because it can be changed into a prime (21043542437) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5260885607 + ... + 5260885610.

Almost surely, 2^21043542434 is an apocalyptic number.

21043542434 is a deficient number, since it is larger than the sum of its proper divisors (10521771220).

21043542434 is a wasteful number, since it uses less digits than its factorization.

21043542434 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10521771219.

The product of its (nonzero) digits is 46080, while the sum is 32.

The spelling of 21043542434 in words is "twenty-one billion, forty-three million, five hundred forty-two thousand, four hundred thirty-four".