21002778499 has 4 divisors (see below), whose sum is σ = 21008503440. Its totient is φ = 20997053560.

The previous prime is 21002778479. The next prime is 21002778539. The reversal of 21002778499 is 99487720012.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21002778499 - 2⁹ = 21002777987 is a prime.

It is a super-3 number, since 3×21002778499³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21002778439) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2856964 + ... + 2864305.

It is an arithmetic number, because the mean of its divisors is an integer number (5252125860).

Almost surely, 2^21002778499 is an apocalyptic number.

21002778499 is a deficient number, since it is larger than the sum of its proper divisors (5724941).

21002778499 is an equidigital number, since it uses as much as digits as its factorization.

21002778499 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5724940.

The product of its (nonzero) digits is 508032, while the sum is 49.

The spelling of 21002778499 in words is "twenty-one billion, two million, seven hundred seventy-eight thousand, four hundred ninety-nine".