21145103251 has 4 divisors (see below), whose sum is σ = 22388932872. Its totient is φ = 19901273632.

The previous prime is 21145103233. The next prime is 21145103261. The reversal of 21145103251 is 15230154112.

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 21145103251 - 2¹⁷ = 21144972179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21145103201) 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, 621914785 + ... + 621914818.

It is an arithmetic number, because the mean of its divisors is an integer number (5597233218).

Almost surely, 2^21145103251 is an apocalyptic number.

21145103251 is a deficient number, since it is larger than the sum of its proper divisors (1243829621).

21145103251 is a wasteful number, since it uses less digits than its factorization.

21145103251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1243829620.

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

Adding to 21145103251 its reverse (15230154112), we get a palindrome (36375257363).

The spelling of 21145103251 in words is "twenty-one billion, one hundred forty-five million, one hundred three thousand, two hundred fifty-one".