691793021 has 4 divisors (see below), whose sum is σ = 728203200. Its totient is φ = 655382844.

The previous prime is 691792963. The next prime is 691793051. The reversal of 691793021 is 120397196.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 691793021 - 2⁶ = 691792957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691793051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18205061 + ... + 18205098.

It is an arithmetic number, because the mean of its divisors is an integer number (182050800).

Almost surely, 2^691793021 is an apocalyptic number.

It is an amenable number.

691793021 is a deficient number, since it is larger than the sum of its proper divisors (36410179).

691793021 is a wasteful number, since it uses less digits than its factorization.

691793021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36410178.

The product of its (nonzero) digits is 20412, while the sum is 38.

The square root of 691793021 is about 26301.9585012219. The cubic root of 691793021 is about 884.4203471210.

The spelling of 691793021 in words is "six hundred ninety-one million, seven hundred ninety-three thousand, twenty-one".