21030423251 has 4 divisors (see below), whose sum is σ = 21181721400. Its totient is φ = 20879125104.

The previous prime is 21030423241. The next prime is 21030423259. The reversal of 21030423251 is 15232403012.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21030423251 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21030423259) 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 3 ways as a sum of consecutive naturals, for example, 75648866 + ... + 75649143.

It is an arithmetic number, because the mean of its divisors is an integer number (5295430350).

Almost surely, 2^21030423251 is an apocalyptic number.

21030423251 is a deficient number, since it is larger than the sum of its proper divisors (151298149).

21030423251 is a wasteful number, since it uses less digits than its factorization.

21030423251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151298148.

The product of its (nonzero) digits is 1440, while the sum is 23.

Adding to 21030423251 its reverse (15232403012), we get a palindrome (36262826263).

The spelling of 21030423251 in words is "twenty-one billion, thirty million, four hundred twenty-three thousand, two hundred fifty-one".