21021232421 has 8 divisors (see below), whose sum is σ = 25068799104. Its totient is φ = 17234799120.

The previous prime is 21021232409. The next prime is 21021232423. The reversal of 21021232421 is 12423212012.

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

It is a de Polignac number, because none of the positive numbers 2^k-21021232421 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021232393 and 21021232402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021232423) 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, 65283170 + ... + 65283491.

It is an arithmetic number, because the mean of its divisors is an integer number (3133599888).

Almost surely, 2^21021232421 is an apocalyptic number.

It is an amenable number.

21021232421 is a deficient number, since it is larger than the sum of its proper divisors (4047566683).

21021232421 is a wasteful number, since it uses less digits than its factorization.

21021232421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 130566691.

The product of its (nonzero) digits is 384, while the sum is 20.

Adding to 21021232421 its reverse (12423212012), we get a palindrome (33444444433).

The spelling of 21021232421 in words is "twenty-one billion, twenty-one million, two hundred thirty-two thousand, four hundred twenty-one".