21251021021 has 8 divisors (see below), whose sum is σ = 21555177024. Its totient is φ = 20947217760.

The previous prime is 21251021009. The next prime is 21251021039. The reversal of 21251021021 is 12012015212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21251021021 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251026021) 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 7 ways as a sum of consecutive naturals, for example, 34376 + ... + 209006.

It is an arithmetic number, because the mean of its divisors is an integer number (2694397128).

Almost surely, 2^21251021021 is an apocalyptic number.

It is an amenable number.

21251021021 is a deficient number, since it is larger than the sum of its proper divisors (304156003).

21251021021 is a wasteful number, since it uses less digits than its factorization.

21251021021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176371.

The product of its (nonzero) digits is 80, while the sum is 17.

Adding to 21251021021 its reverse (12012015212), we get a palindrome (33263036233).

The spelling of 21251021021 in words is "twenty-one billion, two hundred fifty-one million, twenty-one thousand, twenty-one".