691395021399 has 16 divisors (see below), whose sum is σ = 939944028384. Its totient is φ = 451900800000.

The previous prime is 691395021397. The next prime is 691395021403. The reversal of 691395021399 is 993120593196.

It is a happy number.

It is not a de Polignac number, because 691395021399 - 2¹ = 691395021397 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691395021397) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1381102 + ... + 1813899.

It is an arithmetic number, because the mean of its divisors is an integer number (58746501774).

Almost surely, 2^691395021399 is an apocalyptic number.

691395021399 is a deficient number, since it is larger than the sum of its proper divisors (248549006985).

691395021399 is a wasteful number, since it uses less digits than its factorization.

691395021399 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3196418.

The product of its (nonzero) digits is 3542940, while the sum is 57.

The spelling of 691395021399 in words is "six hundred ninety-one billion, three hundred ninety-five million, twenty-one thousand, three hundred ninety-nine".