689991509 has 2 divisors, whose sum is σ = 689991510. Its totient is φ = 689991508.

The previous prime is 689991493. The next prime is 689991553. The reversal of 689991509 is 905199986.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 647702500 + 42289009 = 25450^2 + 6503^2 .

It is a cyclic number.

It is not a de Polignac number, because 689991509 - 2⁴ = 689991493 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (689991569) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 344995754 + 344995755.

It is an arithmetic number, because the mean of its divisors is an integer number (344995755).

Almost surely, 2^689991509 is an apocalyptic number.

It is an amenable number.

689991509 is a deficient number, since it is larger than the sum of its proper divisors (1).

689991509 is an equidigital number, since it uses as much as digits as its factorization.

689991509 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1574640, while the sum is 56.

The square root of 689991509 is about 26267.6894492074. The cubic root of 689991509 is about 883.6519675300.

The spelling of 689991509 in words is "six hundred eighty-nine million, nine hundred ninety-one thousand, five hundred nine".