691651 has 2 divisors, whose sum is σ = 691652. Its totient is φ = 691650.

The previous prime is 691637. The next prime is 691661. The reversal of 691651 is 156196.

691651 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 691651 - 2¹¹ = 689603 is a prime.

It is a super-2 number, since 2×691651² = 956762211602, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (691631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345825 + 345826.

It is an arithmetic number, because the mean of its divisors is an integer number (345826).

2⁶⁹¹⁶⁵¹ is an apocalyptic number.

691651 is a deficient number, since it is larger than the sum of its proper divisors (1).

691651 is an equidigital number, since it uses as much as digits as its factorization.

691651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1620, while the sum is 28.

The square root of 691651 is about 831.6555777484. The cubic root of 691651 is about 88.4359820897.

The spelling of 691651 in words is "six hundred ninety-one thousand, six hundred fifty-one".