21193831 has 2 divisors, whose sum is σ = 21193832. Its totient is φ = 21193830.

The previous prime is 21193829. The next prime is 21193841. The reversal of 21193831 is 13839112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21193831 - 2¹ = 21193829 is a prime.

It is a super-2 number, since 2×21193831² = 898356944913122, which contains 22 as substring.

Together with 21193829, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21193831.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21193841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10596915 + 10596916.

It is an arithmetic number, because the mean of its divisors is an integer number (10596916).

Almost surely, 2^21193831 is an apocalyptic number.

21193831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21193831 is an equidigital number, since it uses as much as digits as its factorization.

21193831 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1296, while the sum is 28.

The square root of 21193831 is about 4603.6758139556. The cubic root of 21193831 is about 276.7386527413.

The spelling of 21193831 in words is "twenty-one million, one hundred ninety-three thousand, eight hundred thirty-one".