21253737506 has 8 divisors (see below), whose sum is σ = 32742244380. Its totient is φ = 10339656048.

The previous prime is 21253737487. The next prime is 21253737511. The reversal of 21253737506 is 60573735212.

It can be written as a sum of positive squares in 2 ways, for example, as 20969646481 + 284091025 = 144809^2 + 16855^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21253737506² (a number of 21 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 143606261 + ... + 143606408.

Almost surely, 2^21253737506 is an apocalyptic number.

21253737506 is a deficient number, since it is larger than the sum of its proper divisors (11488506874).

21253737506 is a wasteful number, since it uses less digits than its factorization.

21253737506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 287212708.

The product of its (nonzero) digits is 264600, while the sum is 41.

The spelling of 21253737506 in words is "twenty-one billion, two hundred fifty-three million, seven hundred thirty-seven thousand, five hundred six".