21779488397987 has 4 divisors (see below), whose sum is σ = 21782546892456. Its totient is φ = 21776429903520.

The previous prime is 21779488397981. The next prime is 21779488398029. The reversal of 21779488397987 is 78979388497712.

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 21779488397987 - 2¹⁶ = 21779488332451 is a prime.

It is a super-2 number, since 2×21779488397987² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21779488397981) 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, 1529236553 + ... + 1529250794.

It is an arithmetic number, because the mean of its divisors is an integer number (5445636723114).

Almost surely, 2^{21779488397987} is an apocalyptic number.

21779488397987 is a deficient number, since it is larger than the sum of its proper divisors (3058494469).

21779488397987 is an equidigital number, since it uses as much as digits as its factorization.

21779488397987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3058494468.

The product of its digits is 21508042752, while the sum is 89.

The spelling of 21779488397987 in words is "twenty-one trillion, seven hundred seventy-nine billion, four hundred eighty-eight million, three hundred ninety-seven thousand, nine hundred eighty-seven".