21642243661387 has 2 divisors, whose sum is σ = 21642243661388. Its totient is φ = 21642243661386.

The previous prime is 21642243661361. The next prime is 21642243661429. The reversal of 21642243661387 is 78316634224612.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21642243661387 is a prime.

It is a super-4 number, since 4×21642243661387⁴ (a number of 54 digits) contains 4444 as substring.

It is not a weakly prime, because it can be changed into another prime (21642243661487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10821121830693 + 10821121830694.

It is an arithmetic number, because the mean of its divisors is an integer number (10821121830694).

Almost surely, 2^{21642243661387} is an apocalyptic number.

21642243661387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21642243661387 is an equidigital number, since it uses as much as digits as its factorization.

21642243661387 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 13934592, while the sum is 55.

Adding to 21642243661387 its reverse (78316634224612), we get a palindrome (99958877885999).

The spelling of 21642243661387 in words is "twenty-one trillion, six hundred forty-two billion, two hundred forty-three million, six hundred sixty-one thousand, three hundred eighty-seven".