21125223251 has 16 divisors (see below), whose sum is σ = 23522555520. Its totient is φ = 18811404480.

The previous prime is 21125223239. The next prime is 21125223257. The reversal of 21125223251 is 15232252112.

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-21125223251 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 21125223251.

It is not an unprimeable number, because it can be changed into a prime (21125223257) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3920 + ... + 205586.

It is an arithmetic number, because the mean of its divisors is an integer number (1470159720).

Almost surely, 2^21125223251 is an apocalyptic number.

21125223251 is a deficient number, since it is larger than the sum of its proper divisors (2397332269).

21125223251 is a wasteful number, since it uses less digits than its factorization.

21125223251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 201874.

The product of its digits is 2400, while the sum is 26.

Adding to 21125223251 its reverse (15232252112), we get a palindrome (36357475363).

The spelling of 21125223251 in words is "twenty-one billion, one hundred twenty-five million, two hundred twenty-three thousand, two hundred fifty-one".