155637661 has 2 divisors, whose sum is σ = 155637662. Its totient is φ = 155637660.

The previous prime is 155637659. The next prime is 155637689. The reversal of 155637661 is 166736551.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 92736900 + 62900761 = 9630^2 + 7931^2 .

It is an emirp because it is prime and its reverse (166736551) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 155637661 - 2¹ = 155637659 is a prime.

Together with 155637659, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155637631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77818830 + 77818831.

It is an arithmetic number, because the mean of its divisors is an integer number (77818831).

Almost surely, 2^155637661 is an apocalyptic number.

It is an amenable number.

155637661 is a deficient number, since it is larger than the sum of its proper divisors (1).

155637661 is an equidigital number, since it uses as much as digits as its factorization.

155637661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 113400, while the sum is 40.

The square root of 155637661 is about 12475.4823954827. The cubic root of 155637661 is about 537.9041543719.

The spelling of 155637661 in words is "one hundred fifty-five million, six hundred thirty-seven thousand, six hundred sixty-one".