155105021 has 4 divisors (see below), whose sum is σ = 160453500. Its totient is φ = 149756544.

The previous prime is 155104981. The next prime is 155105051. The reversal of 155105021 is 120501551.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 32205625 + 122899396 = 5675^2 + 11086^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-155105021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 155104984 and 155105002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155105051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2674196 + ... + 2674253.

It is an arithmetic number, because the mean of its divisors is an integer number (40113375).

Almost surely, 2^155105021 is an apocalyptic number.

It is an amenable number.

155105021 is a deficient number, since it is larger than the sum of its proper divisors (5348479).

155105021 is an equidigital number, since it uses as much as digits as its factorization.

155105021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5348478.

The product of its (nonzero) digits is 250, while the sum is 20.

The square root of 155105021 is about 12454.1166286493. The cubic root of 155105021 is about 537.2898284845.

Adding to 155105021 its reverse (120501551), we get a palindrome (275606572).

The spelling of 155105021 in words is "one hundred fifty-five million, one hundred five thousand, twenty-one".