21531103251 has 16 divisors (see below), whose sum is σ = 32813318400. Its totient is φ = 12301980768.

The previous prime is 21531103241. The next prime is 21531103261. The reversal of 21531103251 is 15230113512.

It is an interprime number because it is at equal distance from previous prime (21531103241) and next prime (21531103261).

It is not a de Polignac number, because 21531103251 - 2²¹ = 21529006099 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21531103201) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 125965 + ... + 242753.

It is an arithmetic number, because the mean of its divisors is an integer number (2050832400).

Almost surely, 2^21531103251 is an apocalyptic number.

21531103251 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21531103251 is a deficient number, since it is larger than the sum of its proper divisors (11282215149).

21531103251 is a wasteful number, since it uses less digits than its factorization.

21531103251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125578.

The product of its (nonzero) digits is 900, while the sum is 24.

Adding to 21531103251 its reverse (15230113512), we get a palindrome (36761216763).

The spelling of 21531103251 in words is "twenty-one billion, five hundred thirty-one million, one hundred three thousand, two hundred fifty-one".