21931281351 has 12 divisors (see below), whose sum is σ = 36204020112. Its totient is φ = 12532160736.

The previous prime is 21931281313. The next prime is 21931281389. The reversal of 21931281351 is 15318213912.

21931281351 is a `hidden beast` number, since 21 + 9 + 3 + 1 + 281 + 351 = 666.

It is an interprime number because it is at equal distance from previous prime (21931281313) and next prime (21931281389).

It is not a de Polignac number, because 21931281351 - 2¹⁸ = 21931019207 is a prime.

It is a super-2 number, since 2×21931281351² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21931281301) 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 11 ways as a sum of consecutive naturals, for example, 174057726 + ... + 174057851.

It is an arithmetic number, because the mean of its divisors is an integer number (3017001676).

Almost surely, 2^21931281351 is an apocalyptic number.

21931281351 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21931281351 is a deficient number, since it is larger than the sum of its proper divisors (14272738761).

21931281351 is a wasteful number, since it uses less digits than its factorization.

21931281351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 348115590 (or 348115587 counting only the distinct ones).

The product of its digits is 12960, while the sum is 36.

The spelling of 21931281351 in words is "twenty-one billion, nine hundred thirty-one million, two hundred eighty-one thousand, three hundred fifty-one".