21165403250 has 32 divisors (see below), whose sum is σ = 39786153264. Its totient is φ = 8431008000.

The previous prime is 21165403219. The next prime is 21165403271. The reversal of 21165403250 is 5230456112.

It can be written as a sum of positive squares in 8 ways, for example, as 6083844001 + 15081559249 = 77999^2 + 122807^2 .

It is a super-2 number, since 2×21165403250² (a number of 21 digits) contains 22 as substring.

It is a Curzon number.

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 in 15 ways as a sum of consecutive naturals, for example, 115397 + ... + 235896.

Almost surely, 2^21165403250 is an apocalyptic number.

21165403250 is a deficient number, since it is larger than the sum of its proper divisors (18620750014).

21165403250 is a wasteful number, since it uses less digits than its factorization.

21165403250 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 351551 (or 351541 counting only the distinct ones).

The product of its (nonzero) digits is 7200, while the sum is 29.

Adding to 21165403250 its reverse (5230456112), we get a palindrome (26395859362).

The spelling of 21165403250 in words is "twenty-one billion, one hundred sixty-five million, four hundred three thousand, two hundred fifty".