21636331 has 2 divisors, whose sum is σ = 21636332. Its totient is φ = 21636330.

The previous prime is 21636319. The next prime is 21636341. The reversal of 21636331 is 13363612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21636331 - 2⁷ = 21636203 is a prime.

It is a super-2 number, since 2×21636331² = 936261638283122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21636296 and 21636305.

It is not a weakly prime, because it can be changed into another prime (21636301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10818165 + 10818166.

It is an arithmetic number, because the mean of its divisors is an integer number (10818166).

Almost surely, 2^21636331 is an apocalyptic number.

21636331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21636331 is an equidigital number, since it uses as much as digits as its factorization.

21636331 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1944, while the sum is 25.

The square root of 21636331 is about 4651.4869665517. The cubic root of 21636331 is about 278.6513847440.

Adding to 21636331 its reverse (13363612), we get a palindrome (34999943).

The spelling of 21636331 in words is "twenty-one million, six hundred thirty-six thousand, three hundred thirty-one".