689811851521 has 4 divisors (see below), whose sum is σ = 742874301652. Its totient is φ = 636749401392.

The previous prime is 689811851489. The next prime is 689811851543. The reversal of 689811851521 is 125158118986.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 90457179121 + 599354672400 = 300761^2 + 774180^2 .

It is not a de Polignac number, because 689811851521 - 2⁵ = 689811851489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (689811851321) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26531225046 + ... + 26531225071.

It is an arithmetic number, because the mean of its divisors is an integer number (185718575413).

Almost surely, 2^689811851521 is an apocalyptic number.

It is an amenable number.

689811851521 is a deficient number, since it is larger than the sum of its proper divisors (53062450131).

689811851521 is a wasteful number, since it uses less digits than its factorization.

689811851521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53062450130.

The product of its digits is 1382400, while the sum is 55.

The spelling of 689811851521 in words is "six hundred eighty-nine billion, eight hundred eleven million, eight hundred fifty-one thousand, five hundred twenty-one".