690487821 has 20 divisors (see below), whose sum is σ = 1059351612. Its totient is φ = 447882048.

The previous prime is 690487789. The next prime is 690487823. The reversal of 690487821 is 128784096.

690487821 is a `hidden beast` number, since 6 + 90 + 487 + 82 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 348755625 + 341732196 = 18675^2 + 18486^2 .

It is not a de Polignac number, because 690487821 - 2⁵ = 690487789 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (690487823) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 112200 + ... + 118193.

Almost surely, 2^690487821 is an apocalyptic number.

It is an amenable number.

690487821 is a deficient number, since it is larger than the sum of its proper divisors (368863791).

690487821 is a wasteful number, since it uses less digits than its factorization.

690487821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 230442 (or 230433 counting only the distinct ones).

The product of its (nonzero) digits is 193536, while the sum is 45.

The square root of 690487821 is about 26277.1349465652. The cubic root of 690487821 is about 883.8637875102.

The spelling of 690487821 in words is "six hundred ninety million, four hundred eighty-seven thousand, eight hundred twenty-one".