21308031 has 12 divisors (see below), whose sum is σ = 30964752. Its totient is φ = 14119296.

The previous prime is 21308029. The next prime is 21308047. The reversal of 21308031 is 13080312.

It is not a de Polignac number, because 21308031 - 2¹ = 21308029 is a prime.

It is a super-2 number, since 2×21308031² = 908064370193922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21307995 and 21308013.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308081) 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 11 ways as a sum of consecutive naturals, for example, 5586 + ... + 8591.

It is an arithmetic number, because the mean of its divisors is an integer number (2580396).

Almost surely, 2^21308031 is an apocalyptic number.

21308031 is a deficient number, since it is larger than the sum of its proper divisors (9656721).

21308031 is a wasteful number, since it uses less digits than its factorization.

21308031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14350 (or 14347 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21308031 is about 4616.0622829420. The cubic root of 21308031 is about 277.2348184995.

Adding to 21308031 its reverse (13080312), we get a palindrome (34388343).

The spelling of 21308031 in words is "twenty-one million, three hundred eight thousand, thirty-one".