21603426251 has 4 divisors (see below), whose sum is σ = 23567374104. Its totient is φ = 19639478400.

The previous prime is 21603426211. The next prime is 21603426283. The reversal of 21603426251 is 15262430612.

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 21603426251 - 2¹⁰ = 21603425227 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21603426211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 981973910 + ... + 981973931.

It is an arithmetic number, because the mean of its divisors is an integer number (5891843526).

Almost surely, 2^21603426251 is an apocalyptic number.

21603426251 is a deficient number, since it is larger than the sum of its proper divisors (1963947853).

21603426251 is a wasteful number, since it uses less digits than its factorization.

21603426251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1963947852.

The product of its (nonzero) digits is 17280, while the sum is 32.

Adding to 21603426251 its reverse (15262430612), we get a palindrome (36865856863).

The spelling of 21603426251 in words is "twenty-one billion, six hundred three million, four hundred twenty-six thousand, two hundred fifty-one".