21420661417 has 4 divisors (see below), whose sum is σ = 21641493076. Its totient is φ = 21199829760.

The previous prime is 21420661411. The next prime is 21420661429. The reversal of 21420661417 is 71416602412.

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

It can be written as a sum of positive squares in 2 ways, for example, as 12437602576 + 8983058841 = 111524^2 + 94779^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21420661417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21420661411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 110415684 + ... + 110415877.

It is an arithmetic number, because the mean of its divisors is an integer number (5410373269).

Almost surely, 2^21420661417 is an apocalyptic number.

It is an amenable number.

21420661417 is a deficient number, since it is larger than the sum of its proper divisors (220831659).

21420661417 is an equidigital number, since it uses as much as digits as its factorization.

21420661417 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220831658.

The product of its (nonzero) digits is 16128, while the sum is 34.

The spelling of 21420661417 in words is "twenty-one billion, four hundred twenty million, six hundred sixty-one thousand, four hundred seventeen".