20999999 has 2 divisors, whose sum is σ = 21000000. Its totient is φ = 20999998.

The previous prime is 20999977. The next prime is 21000037. The reversal of 20999999 is 99999902.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 20999999 - 2¹² = 20995903 is a prime.

It is a Chen prime.

20999999 is a modest number, since divided by 9999 gives 2099 as remainder.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20999939) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10499999 + 10500000.

It is an arithmetic number, because the mean of its divisors is an integer number (10500000).

Almost surely, 2^20999999 is an apocalyptic number.

20999999 is a deficient number, since it is larger than the sum of its proper divisors (1).

20999999 is an equidigital number, since it uses as much as digits as its factorization.

20999999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1062882, while the sum is 56.

The square root of 20999999 is about 4582.5755858469. The cubic root of 20999999 is about 275.8924132589.

The spelling of 20999999 in words is "twenty million, nine hundred ninety-nine thousand, nine hundred ninety-nine".