161556553 has 2 divisors, whose sum is σ = 161556554. Its totient is φ = 161556552.

The previous prime is 161556517. The next prime is 161556583. The reversal of 161556553 is 355655161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 103978809 + 57577744 = 10197^2 + 7588^2 .

It is a cyclic number.

It is not a de Polignac number, because 161556553 - 2²¹ = 159459401 is a prime.

It is a super-2 number, since 2×161556553² = 52201039634483618, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (161556583) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80778276 + 80778277.

It is an arithmetic number, because the mean of its divisors is an integer number (80778277).

Almost surely, 2^161556553 is an apocalyptic number.

It is an amenable number.

161556553 is a deficient number, since it is larger than the sum of its proper divisors (1).

161556553 is an equidigital number, since it uses as much as digits as its factorization.

161556553 is an evil number, because the sum of its binary digits is even.

The product of its digits is 67500, while the sum is 37.

The square root of 161556553 is about 12710.4898804098. The cubic root of 161556553 is about 544.6383179492.

The spelling of 161556553 in words is "one hundred sixty-one million, five hundred fifty-six thousand, five hundred fifty-three".