21381433 has 2 divisors, whose sum is σ = 21381434. Its totient is φ = 21381432.

The previous prime is 21381407. The next prime is 21381457. The reversal of 21381433 is 33418312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21270544 + 110889 = 4612^2 + 333^2 .

It is a cyclic number.

It is not a de Polignac number, because 21381433 - 2⁹ = 21380921 is a prime.

It is equal to p_1352554 and since 21381433 and 1352554 have the same sum of digits, it is a Honaker prime.

It is a junction number, because it is equal to n+sod(n) for n = 21381398 and 21381407.

It is not a weakly prime, because it can be changed into another prime (21381133) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10690716 + 10690717.

It is an arithmetic number, because the mean of its divisors is an integer number (10690717).

Almost surely, 2^21381433 is an apocalyptic number.

It is an amenable number.

21381433 is a deficient number, since it is larger than the sum of its proper divisors (1).

21381433 is an equidigital number, since it uses as much as digits as its factorization.

21381433 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1728, while the sum is 25.

The square root of 21381433 is about 4624.0061634907. The cubic root of 21381433 is about 277.5527935700.

Adding to 21381433 its reverse (33418312), we get a palindrome (54799745).

The spelling of 21381433 in words is "twenty-one million, three hundred eighty-one thousand, four hundred thirty-three".