21649799 has 2 divisors, whose sum is σ = 21649800. Its totient is φ = 21649798.

The previous prime is 21649757. The next prime is 21649819. The reversal of 21649799 is 99794612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21649799 - 2⁸ = 21649543 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 (21649499) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10824899 + 10824900.

It is an arithmetic number, because the mean of its divisors is an integer number (10824900).

Almost surely, 2^21649799 is an apocalyptic number.

21649799 is a deficient number, since it is larger than the sum of its proper divisors (1).

21649799 is an equidigital number, since it uses as much as digits as its factorization.

21649799 is an evil number, because the sum of its binary digits is even.

The product of its digits is 244944, while the sum is 47.

The square root of 21649799 is about 4652.9344504302. The cubic root of 21649799 is about 278.7091902693.

The spelling of 21649799 in words is "twenty-one million, six hundred forty-nine thousand, seven hundred ninety-nine".