155542021 has 2 divisors, whose sum is σ = 155542022. Its totient is φ = 155542020.

The previous prime is 155542003. The next prime is 155542033. The reversal of 155542021 is 120245551.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 134884996 + 20657025 = 11614^2 + 4545^2 .

It is a cyclic number.

It is not a de Polignac number, because 155542021 - 2¹⁵ = 155509253 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155542001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 77771010 + 77771011.

It is an arithmetic number, because the mean of its divisors is an integer number (77771011).

Almost surely, 2^155542021 is an apocalyptic number.

It is an amenable number.

155542021 is a deficient number, since it is larger than the sum of its proper divisors (1).

155542021 is an equidigital number, since it uses as much as digits as its factorization.

155542021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2000, while the sum is 25.

The square root of 155542021 is about 12471.6486881246. The cubic root of 155542021 is about 537.7939503370.

Adding to 155542021 its reverse (120245551), we get a palindrome (275787572).

The spelling of 155542021 in words is "one hundred fifty-five million, five hundred forty-two thousand, twenty-one".