1555380661 has 2 divisors, whose sum is σ = 1555380662. Its totient is φ = 1555380660.

The previous prime is 1555380653. The next prime is 1555380667. The reversal of 1555380661 is 1660835551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1010858436 + 544522225 = 31794^2 + 23335^2 .

It is a cyclic number.

It is not a de Polignac number, because 1555380661 - 2³ = 1555380653 is a prime.

It is a super-2 number, since 2×1555380661² = 4838418001225593842, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1555380667) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 777690330 + 777690331.

It is an arithmetic number, because the mean of its divisors is an integer number (777690331).

Almost surely, 2^1555380661 is an apocalyptic number.

It is an amenable number.

1555380661 is a deficient number, since it is larger than the sum of its proper divisors (1).

1555380661 is an equidigital number, since it uses as much as digits as its factorization.

1555380661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108000, while the sum is 40.

The square root of 1555380661 is about 39438.3146318399. The cubic root of 1555380661 is about 1158.6321225154.

The spelling of 1555380661 in words is "one billion, five hundred fifty-five million, three hundred eighty thousand, six hundred sixty-one".