21042407 has 2 divisors, whose sum is σ = 21042408. Its totient is φ = 21042406.

The previous prime is 21042383. The next prime is 21042419. The reversal of 21042407 is 70424012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21042407 - 2²² = 16848103 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21042457) 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, 10521203 + 10521204.

It is an arithmetic number, because the mean of its divisors is an integer number (10521204).

Almost surely, 2^21042407 is an apocalyptic number.

21042407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21042407 is an equidigital number, since it uses as much as digits as its factorization.

21042407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 448, while the sum is 20.

The square root of 21042407 is about 4587.2003444367. The cubic root of 21042407 is about 276.0780034024.

Adding to 21042407 its reverse (70424012), we get a palindrome (91466419).

The spelling of 21042407 in words is "twenty-one million, forty-two thousand, four hundred seven".