21906407 has 2 divisors, whose sum is σ = 21906408. Its totient is φ = 21906406.

The previous prime is 21906389. The next prime is 21906413. The reversal of 21906407 is 70460912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21906407 - 2⁸ = 21906151 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21906407.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21906007) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10953203 + 10953204.

It is an arithmetic number, because the mean of its divisors is an integer number (10953204).

Almost surely, 2^21906407 is an apocalyptic number.

21906407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21906407 is an equidigital number, since it uses as much as digits as its factorization.

21906407 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 21906407 is about 4680.4280787125. The cubic root of 21906407 is about 279.8060178524.

The spelling of 21906407 in words is "twenty-one million, nine hundred six thousand, four hundred seven".