155638421 has 2 divisors, whose sum is σ = 155638422. Its totient is φ = 155638420.

The previous prime is 155638393. The next prime is 155638423. The reversal of 155638421 is 124836551.

155638421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 139948900 + 15689521 = 11830^2 + 3961^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-155638421 is a prime.

Together with 155638423, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155638423) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77819210 + 77819211.

It is an arithmetic number, because the mean of its divisors is an integer number (77819211).

Almost surely, 2^155638421 is an apocalyptic number.

It is an amenable number.

155638421 is a deficient number, since it is larger than the sum of its proper divisors (1).

155638421 is an equidigital number, since it uses as much as digits as its factorization.

155638421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 28800, while the sum is 35.

The square root of 155638421 is about 12475.5128551896. The cubic root of 155638421 is about 537.9050299237.

The spelling of 155638421 in words is "one hundred fifty-five million, six hundred thirty-eight thousand, four hundred twenty-one".