21840407 has 2 divisors, whose sum is σ = 21840408. Its totient is φ = 21840406.

The previous prime is 21840391. The next prime is 21840421. The reversal of 21840407 is 70404812.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21840407 - 2⁴ = 21840391 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 (21840457) 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, 10920203 + 10920204.

It is an arithmetic number, because the mean of its divisors is an integer number (10920204).

Almost surely, 2^21840407 is an apocalyptic number.

21840407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21840407 is an equidigital number, since it uses as much as digits as its factorization.

21840407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1792, while the sum is 26.

The square root of 21840407 is about 4673.3721229964. The cubic root of 21840407 is about 279.5247337151.

The spelling of 21840407 in words is "twenty-one million, eight hundred forty thousand, four hundred seven".