21155399 has 2 divisors, whose sum is σ = 21155400. Its totient is φ = 21155398.

The previous prime is 21155371. The next prime is 21155411. The reversal of 21155399 is 99355112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21155399 - 2¹² = 21151303 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 (21155339) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577699 + 10577700.

It is an arithmetic number, because the mean of its divisors is an integer number (10577700).

Almost surely, 2^21155399 is an apocalyptic number.

21155399 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155399 is an equidigital number, since it uses as much as digits as its factorization.

21155399 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12150, while the sum is 35.

The square root of 21155399 is about 4599.4998641157. The cubic root of 21155399 is about 276.5712761257.

The spelling of 21155399 in words is "twenty-one million, one hundred fifty-five thousand, three hundred ninety-nine".