21286531643506 has 8 divisors (see below), whose sum is σ = 31929848312940. Its totient is φ = 10643248872528.

The previous prime is 21286531643353. The next prime is 21286531643549. The reversal of 21286531643506 is 60534613568212.

It can be written as a sum of positive squares in 2 ways, for example, as 12826490425281 + 8460041218225 = 3581409^2 + 2908615^2 .

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

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, 6841821 + ... + 9454288.

Almost surely, 2^{21286531643506} is an apocalyptic number.

21286531643506 is a deficient number, since it is larger than the sum of its proper divisors (10643316669434).

21286531643506 is a wasteful number, since it uses less digits than its factorization.

21286531643506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16949228.

The product of its (nonzero) digits is 6220800, while the sum is 52.

The spelling of 21286531643506 in words is "twenty-one trillion, two hundred eighty-six billion, five hundred thirty-one million, six hundred forty-three thousand, five hundred six".