1640657 has 2 divisors, whose sum is σ = 1640658. Its totient is φ = 1640656.

The previous prime is 1640641. The next prime is 1640663. The reversal of 1640657 is 7560461.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1560001 + 80656 = 1249^2 + 284^2 .

It is a cyclic number.

It is not a de Polignac number, because 1640657 - 2⁴ = 1640641 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1640677) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 820328 + 820329.

It is an arithmetic number, because the mean of its divisors is an integer number (820329).

2^1640657 is an apocalyptic number.

It is an amenable number.

1640657 is a deficient number, since it is larger than the sum of its proper divisors (1).

1640657 is an equidigital number, since it uses as much as digits as its factorization.

1640657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5040, while the sum is 29.

The square root of 1640657 is about 1280.8813372050. The cubic root of 1640657 is about 117.9431163154.

The spelling of 1640657 in words is "one million, six hundred forty thousand, six hundred fifty-seven".