21004430786 has 4 divisors (see below), whose sum is σ = 31506646182. Its totient is φ = 10502215392.

The previous prime is 21004430779. The next prime is 21004430827. The reversal of 21004430786 is 68703440012.

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

It can be written as a sum of positive squares in only one way, i.e., 20914655161 + 89775625 = 144619^2 + 9475^2 .

It is a super-2 number, since 2×21004430786² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5251107695 + ... + 5251107698.

Almost surely, 2^21004430786 is an apocalyptic number.

21004430786 is a deficient number, since it is larger than the sum of its proper divisors (10502215396).

21004430786 is a wasteful number, since it uses less digits than its factorization.

21004430786 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10502215395.

The product of its (nonzero) digits is 32256, while the sum is 35.

Adding to 21004430786 its reverse (68703440012), we get a palindrome (89707870798).

The spelling of 21004430786 in words is "twenty-one billion, four million, four hundred thirty thousand, seven hundred eighty-six".