688215881 has 2 divisors, whose sum is σ = 688215882. Its totient is φ = 688215880.

The previous prime is 688215809. The next prime is 688215883. The reversal of 688215881 is 188512886.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 409860025 + 278355856 = 20245^2 + 16684^2 .

It is a cyclic number.

It is not a de Polignac number, because 688215881 - 2¹⁸ = 687953737 is a prime.

It is a super-2 number, since 2×688215881² = 947282197721212322, which contains 22 as substring.

Together with 688215883, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (688215883) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344107940 + 344107941.

It is an arithmetic number, because the mean of its divisors is an integer number (344107941).

Almost surely, 2^688215881 is an apocalyptic number.

It is an amenable number.

688215881 is a deficient number, since it is larger than the sum of its proper divisors (1).

688215881 is an equidigital number, since it uses as much as digits as its factorization.

688215881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 245760, while the sum is 47.

The square root of 688215881 is about 26233.8689674245. The cubic root of 688215881 is about 882.8933180849.

The spelling of 688215881 in words is "six hundred eighty-eight million, two hundred fifteen thousand, eight hundred eighty-one".