155732221 has 2 divisors, whose sum is σ = 155732222. Its totient is φ = 155732220.

The previous prime is 155732209. The next prime is 155732281. The reversal of 155732221 is 122237551.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 125328025 + 30404196 = 11195^2 + 5514^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-155732221 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 155732221.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155732281) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77866110 + 77866111.

It is an arithmetic number, because the mean of its divisors is an integer number (77866111).

Almost surely, 2^155732221 is an apocalyptic number.

It is an amenable number.

155732221 is a deficient number, since it is larger than the sum of its proper divisors (1).

155732221 is an equidigital number, since it uses as much as digits as its factorization.

155732221 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4200, while the sum is 28.

The square root of 155732221 is about 12479.2716534259. The cubic root of 155732221 is about 538.0130695682.

Adding to 155732221 its reverse (122237551), we get a palindrome (277969772).

The spelling of 155732221 in words is "one hundred fifty-five million, seven hundred thirty-two thousand, two hundred twenty-one".