21207162815647 has 4 divisors (see below), whose sum is σ = 21212852962336. Its totient is φ = 21201472668960.

The previous prime is 21207162815611. The next prime is 21207162815701. The reversal of 21207162815647 is 74651826170212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21207162815647 - 2⁷ = 21207162815519 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21207162815594 and 21207162815603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21207162015647) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2845067754 + ... + 2845075207.

It is an arithmetic number, because the mean of its divisors is an integer number (5303213240584).

Almost surely, 2^{21207162815647} is an apocalyptic number.

21207162815647 is a deficient number, since it is larger than the sum of its proper divisors (5690146689).

21207162815647 is an equidigital number, since it uses as much as digits as its factorization.

21207162815647 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5690146688.

The product of its (nonzero) digits is 2257920, while the sum is 52.

Adding to 21207162815647 its reverse (74651826170212), we get a palindrome (95858988985859).

The spelling of 21207162815647 in words is "twenty-one trillion, two hundred seven billion, one hundred sixty-two million, eight hundred fifteen thousand, six hundred forty-seven".