21394831 has 4 divisors (see below), whose sum is σ = 21404664. Its totient is φ = 21385000.

The previous prime is 21394829. The next prime is 21394889. The reversal of 21394831 is 13849312.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21394831 - 2¹ = 21394829 is a prime.

It is a super-2 number, since 2×21394831² = 915477587037122, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21394793 and 21394802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21394231) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 40 + ... + 6541.

It is an arithmetic number, because the mean of its divisors is an integer number (5351166).

Almost surely, 2^21394831 is an apocalyptic number.

21394831 is a deficient number, since it is larger than the sum of its proper divisors (9833).

21394831 is an equidigital number, since it uses as much as digits as its factorization.

21394831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9832.

The product of its digits is 5184, while the sum is 31.

The square root of 21394831 is about 4625.4546803531. The cubic root of 21394831 is about 277.6107546972.

The spelling of 21394831 in words is "twenty-one million, three hundred ninety-four thousand, eight hundred thirty-one".