1555661 has 2 divisors, whose sum is σ = 1555662. Its totient is φ = 1555660.

The previous prime is 1555657. The next prime is 1555679. The reversal of 1555661 is 1665551.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 866761 + 688900 = 931^2 + 830^2 .

It is a cyclic number.

It is not a de Polignac number, because 1555661 - 2² = 1555657 is a prime.

It is a super-2 number, since 2×1555661² = 4840162293842, which contains 22 as substring.

It is an Ulam number.

It is a plaindrome in base 16.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1555691) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 777830 + 777831.

It is an arithmetic number, because the mean of its divisors is an integer number (777831).

2^1555661 is an apocalyptic number.

It is an amenable number.

1555661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1555661 is an equidigital number, since it uses as much as digits as its factorization.

1555661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4500, while the sum is 29.

The square root of 1555661 is about 1247.2614000281. The cubic root of 1555661 is about 115.8701728254.

The spelling of 1555661 in words is "one million, five hundred fifty-five thousand, six hundred sixty-one".