21521042421 has 8 divisors (see below), whose sum is σ = 28696915584. Its totient is φ = 14346265440.

The previous prime is 21521042401. The next prime is 21521042453. The reversal of 21521042421 is 12424012512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21521042421 - 2⁶ = 21521042357 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21521042391 and 21521042400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521042401) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 227085 + ... + 307586.

It is an arithmetic number, because the mean of its divisors is an integer number (3587114448).

Almost surely, 2^21521042421 is an apocalyptic number.

It is an amenable number.

21521042421 is a deficient number, since it is larger than the sum of its proper divisors (7175873163).

21521042421 is a wasteful number, since it uses less digits than its factorization.

21521042421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 548091.

The product of its (nonzero) digits is 1280, while the sum is 24.

Adding to 21521042421 its reverse (12424012512), we get a palindrome (33945054933).

The spelling of 21521042421 in words is "twenty-one billion, five hundred twenty-one million, forty-two thousand, four hundred twenty-one".