21686379947 has 2 divisors, whose sum is σ = 21686379948. Its totient is φ = 21686379946.

The previous prime is 21686379943. The next prime is 21686379973. The reversal of 21686379947 is 74997368612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21686379947 - 2² = 21686379943 is a prime.

It is a super-3 number, since 3×21686379947³ (a number of 32 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21686379947.

It is not a weakly prime, because it can be changed into another prime (21686379943) 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 as a sum of consecutive naturals, namely, 10843189973 + 10843189974.

It is an arithmetic number, because the mean of its divisors is an integer number (10843189974).

Almost surely, 2^21686379947 is an apocalyptic number.

21686379947 is a deficient number, since it is larger than the sum of its proper divisors (1).

21686379947 is an equidigital number, since it uses as much as digits as its factorization.

21686379947 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27433728, while the sum is 62.

The spelling of 21686379947 in words is "twenty-one billion, six hundred eighty-six million, three hundred seventy-nine thousand, nine hundred forty-seven".