21140444251 has 4 divisors (see below), whose sum is σ = 21270140392. Its totient is φ = 21010748112.

The previous prime is 21140444207. The next prime is 21140444261. The reversal of 21140444251 is 15244404112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21140444251 - 2⁷ = 21140444123 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21140444261) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64847826 + ... + 64848151.

It is an arithmetic number, because the mean of its divisors is an integer number (5317535098).

Almost surely, 2^21140444251 is an apocalyptic number.

21140444251 is a deficient number, since it is larger than the sum of its proper divisors (129696141).

21140444251 is a wasteful number, since it uses less digits than its factorization.

21140444251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129696140.

The product of its (nonzero) digits is 5120, while the sum is 28.

Adding to 21140444251 its reverse (15244404112), we get a palindrome (36384848363).

The spelling of 21140444251 in words is "twenty-one billion, one hundred forty million, four hundred forty-four thousand, two hundred fifty-one".