21378899 has 2 divisors, whose sum is σ = 21378900. Its totient is φ = 21378898.

The previous prime is 21378883. The next prime is 21378923. The reversal of 21378899 is 99887312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21378899 - 2⁴ = 21378883 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21368899) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10689449 + 10689450.

It is an arithmetic number, because the mean of its divisors is an integer number (10689450).

Almost surely, 2^21378899 is an apocalyptic number.

21378899 is a deficient number, since it is larger than the sum of its proper divisors (1).

21378899 is an equidigital number, since it uses as much as digits as its factorization.

21378899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 217728, while the sum is 47.

The square root of 21378899 is about 4623.7321505468. The cubic root of 21378899 is about 277.5418285025.

The spelling of 21378899 in words is "twenty-one million, three hundred seventy-eight thousand, eight hundred ninety-nine".