21231215251 has 8 divisors (see below), whose sum is σ = 21634763040. Its totient is φ = 20827777152.

The previous prime is 21231215191. The next prime is 21231215261. The reversal of 21231215251 is 15251213212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21231215251 - 2⁷ = 21231215123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21231215261) 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, 437466 + ... + 483568.

It is an arithmetic number, because the mean of its divisors is an integer number (2704345380).

Almost surely, 2^21231215251 is an apocalyptic number.

21231215251 is a deficient number, since it is larger than the sum of its proper divisors (403547789).

21231215251 is an equidigital number, since it uses as much as digits as its factorization.

21231215251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54845.

The product of its digits is 1200, while the sum is 25.

Adding to 21231215251 its reverse (15251213212), we get a palindrome (36482428463).

The spelling of 21231215251 in words is "twenty-one billion, two hundred thirty-one million, two hundred fifteen thousand, two hundred fifty-one".