21109999949 has 2 divisors, whose sum is σ = 21109999950. Its totient is φ = 21109999948.

The previous prime is 21109999921. The next prime is 21109999991. The reversal of 21109999949 is 94999990112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20070388900 + 1039611049 = 141670^2 + 32243^2 .

It is a cyclic number.

It is not a de Polignac number, because 21109999949 - 2¹⁶ = 21109934413 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21109999891 and 21109999900.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21109999919) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10554999974 + 10554999975.

It is an arithmetic number, because the mean of its divisors is an integer number (10554999975).

Almost surely, 2^21109999949 is an apocalyptic number.

It is an amenable number.

21109999949 is a deficient number, since it is larger than the sum of its proper divisors (1).

21109999949 is an equidigital number, since it uses as much as digits as its factorization.

21109999949 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4251528, while the sum is 62.

The spelling of 21109999949 in words is "twenty-one billion, one hundred nine million, nine hundred ninety-nine thousand, nine hundred forty-nine".