921561715687 has 2 divisors, whose sum is σ = 921561715688. Its totient is φ = 921561715686.

The previous prime is 921561715681. The next prime is 921561715729. The reversal of 921561715687 is 786517165129.

It is a weak prime.

It is an emirp because it is prime and its reverse (786517165129) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 921561715687 - 2³⁹ = 371805901799 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (921561715681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 460780857843 + 460780857844.

It is an arithmetic number, because the mean of its divisors is an integer number (460780857844).

Almost surely, 2^921561715687 is an apocalyptic number.

921561715687 is a deficient number, since it is larger than the sum of its proper divisors (1).

921561715687 is an equidigital number, since it uses as much as digits as its factorization.

921561715687 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6350400, while the sum is 58.

The spelling of 921561715687 in words is "nine hundred twenty-one billion, five hundred sixty-one million, seven hundred fifteen thousand, six hundred eighty-seven".