21406507 has 2 divisors, whose sum is σ = 21406508. Its totient is φ = 21406506.

The previous prime is 21406499. The next prime is 21406529. The reversal of 21406507 is 70560412.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21406507 - 2³ = 21406499 is a prime.

It is not a weakly prime, because it can be changed into another prime (21406207) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10703253 + 10703254.

It is an arithmetic number, because the mean of its divisors is an integer number (10703254).

Almost surely, 2^21406507 is an apocalyptic number.

21406507 is a deficient number, since it is larger than the sum of its proper divisors (1).

21406507 is an equidigital number, since it uses as much as digits as its factorization.

21406507 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1680, while the sum is 25.

The square root of 21406507 is about 4626.7166543889. The cubic root of 21406507 is about 277.6612465457.

Adding to 21406507 its reverse (70560412), we get a palindrome (91966919).

The spelling of 21406507 in words is "twenty-one million, four hundred six thousand, five hundred seven".