21645619 has 2 divisors, whose sum is σ = 21645620. Its totient is φ = 21645618.

The previous prime is 21645551. The next prime is 21645683. The reversal of 21645619 is 91654612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21645619 - 2²³ = 13257011 is a prime.

It is a super-2 number, since 2×21645619² = 937065643786322, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21645319) 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, 10822809 + 10822810.

It is an arithmetic number, because the mean of its divisors is an integer number (10822810).

Almost surely, 2^21645619 is an apocalyptic number.

21645619 is a deficient number, since it is larger than the sum of its proper divisors (1).

21645619 is an equidigital number, since it uses as much as digits as its factorization.

21645619 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 12960, while the sum is 34.

The square root of 21645619 is about 4652.4852498423. The cubic root of 21645619 is about 278.6912520057.

The spelling of 21645619 in words is "twenty-one million, six hundred forty-five thousand, six hundred nineteen".