21660407 has 2 divisors, whose sum is σ = 21660408. Its totient is φ = 21660406.

The previous prime is 21660389. The next prime is 21660409. The reversal of 21660407 is 70406612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21660407 - 2⁸ = 21660151 is a prime.

Together with 21660409, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21660409) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10830203 + 10830204.

It is an arithmetic number, because the mean of its divisors is an integer number (10830204).

Almost surely, 2^21660407 is an apocalyptic number.

21660407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21660407 is an equidigital number, since it uses as much as digits as its factorization.

21660407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2016, while the sum is 26.

The square root of 21660407 is about 4654.0742366232. The cubic root of 21660407 is about 278.7547036147.

The spelling of 21660407 in words is "twenty-one million, six hundred sixty thousand, four hundred seven".