1661557 has 2 divisors, whose sum is σ = 1661558. Its totient is φ = 1661556.

The previous prime is 1661549. The next prime is 1661567. The reversal of 1661557 is 7551661.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1661521 + 36 = 1289^2 + 6^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661557 - 2³ = 1661549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661567) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830778 + 830779.

It is an arithmetic number, because the mean of its divisors is an integer number (830779).

2^1661557 is an apocalyptic number.

It is an amenable number.

1661557 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661557 is an equidigital number, since it uses as much as digits as its factorization.

1661557 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 1661557 is about 1289.0139642378. The cubic root of 1661557 is about 118.4418225229.

The spelling of 1661557 in words is "one million, six hundred sixty-one thousand, five hundred fifty-seven".