21535637506 has 4 divisors (see below), whose sum is σ = 32303456262. Its totient is φ = 10767818752.

The previous prime is 21535637503. The next prime is 21535637521. The reversal of 21535637506 is 60573653512.

It is a happy number.

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., 15213002281 + 6322635225 = 123341^2 + 79515^2 .

It is not an unprimeable number, because it can be changed into a prime (21535637503) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5383909375 + ... + 5383909378.

Almost surely, 2^21535637506 is an apocalyptic number.

21535637506 is a deficient number, since it is larger than the sum of its proper divisors (10767818756).

21535637506 is a wasteful number, since it uses less digits than its factorization.

21535637506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10767818755.

The product of its (nonzero) digits is 567000, while the sum is 43.

The spelling of 21535637506 in words is "twenty-one billion, five hundred thirty-five million, six hundred thirty-seven thousand, five hundred six".