21645937 has 2 divisors, whose sum is σ = 21645938. Its totient is φ = 21645936.

The previous prime is 21645907. The next prime is 21646003. The reversal of 21645937 is 73954612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20647936 + 998001 = 4544^2 + 999^2 .

It is a cyclic number.

It is not a de Polignac number, because 21645937 - 2⁷ = 21645809 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21645896 and 21645905.

It is not a weakly prime, because it can be changed into another prime (21645907) 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, 10822968 + 10822969.

It is an arithmetic number, because the mean of its divisors is an integer number (10822969).

Almost surely, 2^21645937 is an apocalyptic number.

It is an amenable number.

21645937 is a deficient number, since it is larger than the sum of its proper divisors (1).

21645937 is an equidigital number, since it uses as much as digits as its factorization.

21645937 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 45360, while the sum is 37.

The square root of 21645937 is about 4652.5194249997. The cubic root of 21645937 is about 278.6926167682.

The spelling of 21645937 in words is "twenty-one million, six hundred forty-five thousand, nine hundred thirty-seven".