21530232251 has 16 divisors (see below), whose sum is σ = 24251443200. Its totient is φ = 18936667200.

The previous prime is 21530232221. The next prime is 21530232257. The reversal of 21530232251 is 15223203512.

It is a happy number.

It is not a de Polignac number, because 21530232251 - 2⁶ = 21530232187 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 21530232251.

It is not an unprimeable number, because it can be changed into a prime (21530232257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2163455 + ... + 2173383.

It is an arithmetic number, because the mean of its divisors is an integer number (1515715200).

Almost surely, 2^21530232251 is an apocalyptic number.

21530232251 is a deficient number, since it is larger than the sum of its proper divisors (2721210949).

21530232251 is a wasteful number, since it uses less digits than its factorization.

21530232251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16330.

The product of its (nonzero) digits is 3600, while the sum is 26.

Adding to 21530232251 its reverse (15223203512), we get a palindrome (36753435763).

The spelling of 21530232251 in words is "twenty-one billion, five hundred thirty million, two hundred thirty-two thousand, two hundred fifty-one".