687639541 has 2 divisors, whose sum is σ = 687639542. Its totient is φ = 687639540.

The previous prime is 687639539. The next prime is 687639553. The reversal of 687639541 is 145936786.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 389904516 + 297735025 = 19746^2 + 17255^2 .

It is a cyclic number.

It is not a de Polignac number, because 687639541 - 2¹ = 687639539 is a prime.

Together with 687639539, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (687639581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 343819770 + 343819771.

It is an arithmetic number, because the mean of its divisors is an integer number (343819771).

Almost surely, 2^687639541 is an apocalyptic number.

It is an amenable number.

687639541 is a deficient number, since it is larger than the sum of its proper divisors (1).

687639541 is an equidigital number, since it uses as much as digits as its factorization.

687639541 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1088640, while the sum is 49.

The square root of 687639541 is about 26222.8820117088. The cubic root of 687639541 is about 882.6467923178.

The spelling of 687639541 in words is "six hundred eighty-seven million, six hundred thirty-nine thousand, five hundred forty-one".