21278899 has 2 divisors, whose sum is σ = 21278900. Its totient is φ = 21278898.

The previous prime is 21278861. The next prime is 21278911. The reversal of 21278899 is 99887212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21278899 - 2¹³ = 21270707 is a prime.

It is not a weakly prime, because it can be changed into another prime (21278819) 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, 10639449 + 10639450.

It is an arithmetic number, because the mean of its divisors is an integer number (10639450).

Almost surely, 2^21278899 is an apocalyptic number.

21278899 is a deficient number, since it is larger than the sum of its proper divisors (1).

21278899 is an equidigital number, since it uses as much as digits as its factorization.

21278899 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 145152, while the sum is 46.

The square root of 21278899 is about 4612.9057003151. The cubic root of 21278899 is about 277.1084172039.

It can be divided in two parts, 212788 and 99, that multiplied together give a palindrome (21066012).

The spelling of 21278899 in words is "twenty-one million, two hundred seventy-eight thousand, eight hundred ninety-nine".