21018362506 has 4 divisors (see below), whose sum is σ = 31527543762. Its totient is φ = 10509181252.

The previous prime is 21018362503. The next prime is 21018362513. The reversal of 21018362506 is 60526381012.

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., 20465877481 + 552485025 = 143059^2 + 23505^2 .

It is not an unprimeable number, because it can be changed into a prime (21018362503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5254590625 + ... + 5254590628.

Almost surely, 2^21018362506 is an apocalyptic number.

21018362506 is a deficient number, since it is larger than the sum of its proper divisors (10509181256).

21018362506 is a wasteful number, since it uses less digits than its factorization.

21018362506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10509181255.

The product of its (nonzero) digits is 17280, while the sum is 34.

The spelling of 21018362506 in words is "twenty-one billion, eighteen million, three hundred sixty-two thousand, five hundred six".