21009407 has 2 divisors, whose sum is σ = 21009408. Its totient is φ = 21009406.

The previous prime is 21009403. The next prime is 21009449. The reversal of 21009407 is 70490012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21009407 - 2² = 21009403 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21009403) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504703 + 10504704.

It is an arithmetic number, because the mean of its divisors is an integer number (10504704).

Almost surely, 2^21009407 is an apocalyptic number.

21009407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009407 is an equidigital number, since it uses as much as digits as its factorization.

21009407 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 21009407 is about 4583.6019678851. The cubic root of 21009407 is about 275.9336070435.

Adding to 21009407 its reverse (70490012), we get a palindrome (91499419).

The spelling of 21009407 in words is "twenty-one million, nine thousand, four hundred seven".