21043542421 has 16 divisors (see below), whose sum is σ = 23983839360. Its totient is φ = 18276477120.

The previous prime is 21043542413. The next prime is 21043542427. The reversal of 21043542421 is 12424534012.

It is not a de Polignac number, because 21043542421 - 2³ = 21043542413 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21043542421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21043542427) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 159571 + ... + 259903.

It is an arithmetic number, because the mean of its divisors is an integer number (1498989960).

Almost surely, 2^21043542421 is an apocalyptic number.

It is an amenable number.

21043542421 is a deficient number, since it is larger than the sum of its proper divisors (2940296939).

21043542421 is a wasteful number, since it uses less digits than its factorization.

21043542421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101196.

The product of its (nonzero) digits is 7680, while the sum is 28.

The spelling of 21043542421 in words is "twenty-one billion, forty-three million, five hundred forty-two thousand, four hundred twenty-one".