861439420721 has 4 divisors (see below), whose sum is σ = 939752095344. Its totient is φ = 783126746100.

The previous prime is 861439420697. The next prime is 861439420727. The reversal of 861439420721 is 127024934168.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 861439420721 - 2¹⁴ = 861439404337 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (861439420727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39156337295 + ... + 39156337316.

It is an arithmetic number, because the mean of its divisors is an integer number (234938023836).

Almost surely, 2^861439420721 is an apocalyptic number.

It is an amenable number.

861439420721 is a deficient number, since it is larger than the sum of its proper divisors (78312674623).

861439420721 is a wasteful number, since it uses less digits than its factorization.

861439420721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78312674622.

The product of its (nonzero) digits is 580608, while the sum is 47.

The spelling of 861439420721 in words is "eight hundred sixty-one billion, four hundred thirty-nine million, four hundred twenty thousand, seven hundred twenty-one".