21142399 has 2 divisors, whose sum is σ = 21142400. Its totient is φ = 21142398.

The previous prime is 21142393. The next prime is 21142423. The reversal of 21142399 is 99324112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21142399 - 2¹¹ = 21140351 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21142399.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21142393) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10571199 + 10571200.

It is an arithmetic number, because the mean of its divisors is an integer number (10571200).

Almost surely, 2^21142399 is an apocalyptic number.

21142399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21142399 is an equidigital number, since it uses as much as digits as its factorization.

21142399 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 31.

The square root of 21142399 is about 4598.0864498180. The cubic root of 21142399 is about 276.5146134694.

The spelling of 21142399 in words is "twenty-one million, one hundred forty-two thousand, three hundred ninety-nine".