1687397861 has 2 divisors, whose sum is σ = 1687397862. Its totient is φ = 1687397860.

The previous prime is 1687397851. The next prime is 1687397897. The reversal of 1687397861 is 1687937861.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1258120900 + 429276961 = 35470^2 + 20719^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1687397861 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1687397797 and 1687397806.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1687397821) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 843698930 + 843698931.

It is an arithmetic number, because the mean of its divisors is an integer number (843698931).

Almost surely, 2^1687397861 is an apocalyptic number.

It is an amenable number.

1687397861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1687397861 is an equidigital number, since it uses as much as digits as its factorization.

1687397861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3048192, while the sum is 56.

The square root of 1687397861 is about 41077.9485977574. The cubic root of 1687397861 is about 1190.5267684091.

The spelling of 1687397861 in words is "one billion, six hundred eighty-seven million, three hundred ninety-seven thousand, eight hundred sixty-one".