1561657 has 2 divisors, whose sum is σ = 1561658. Its totient is φ = 1561656.

The previous prime is 1561639. The next prime is 1561673. The reversal of 1561657 is 7561651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1229881 + 331776 = 1109^2 + 576^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561657 - 2⁷ = 1561529 is a prime.

It is not a weakly prime, because it can be changed into another prime (1561607) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780828 + 780829.

It is an arithmetic number, because the mean of its divisors is an integer number (780829).

2^1561657 is an apocalyptic number.

It is an amenable number.

1561657 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561657 is an equidigital number, since it uses as much as digits as its factorization.

1561657 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6300, while the sum is 31.

The square root of 1561657 is about 1249.6627545062. The cubic root of 1561657 is about 116.0188485028.

The spelling of 1561657 in words is "one million, five hundred sixty-one thousand, six hundred fifty-seven".