71781464971921 has 2 divisors, whose sum is σ = 71781464971922. Its totient is φ = 71781464971920.

The previous prime is 71781464971919. The next prime is 71781464972047. The reversal of 71781464971921 is 12917946418717.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 47485329721600 + 24296135250321 = 6890960^2 + 4929111^2 .

It is a cyclic number.

It is not a de Polignac number, because 71781464971921 - 2¹ = 71781464971919 is a prime.

Together with 71781464971919, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (71781464975921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 35890732485960 + 35890732485961.

It is an arithmetic number, because the mean of its divisors is an integer number (35890732485961).

Almost surely, 2^{71781464971921} is an apocalyptic number.

It is an amenable number.

71781464971921 is a deficient number, since it is larger than the sum of its proper divisors (1).

71781464971921 is an equidigital number, since it uses as much as digits as its factorization.

71781464971921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 42674688, while the sum is 67.

The spelling of 71781464971921 in words is "seventy-one trillion, seven hundred eighty-one billion, four hundred sixty-four million, nine hundred seventy-one thousand, nine hundred twenty-one".