21536831 has 2 divisors, whose sum is σ = 21536832. Its totient is φ = 21536830.

The previous prime is 21536819. The next prime is 21536833. The reversal of 21536831 is 13863512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21536831 is a prime.

It is a super-2 number, since 2×21536831² = 927670179045122, which contains 22 as substring.

Together with 21536833, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21536794 and 21536803.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21536833) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10768415 + 10768416.

It is an arithmetic number, because the mean of its divisors is an integer number (10768416).

Almost surely, 2^21536831 is an apocalyptic number.

21536831 is a deficient number, since it is larger than the sum of its proper divisors (1).

21536831 is an equidigital number, since it uses as much as digits as its factorization.

21536831 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4320, while the sum is 29.

The square root of 21536831 is about 4640.7791371708. The cubic root of 21536831 is about 278.2235792622.

The spelling of 21536831 in words is "twenty-one million, five hundred thirty-six thousand, eight hundred thirty-one".