155406021 has 4 divisors (see below), whose sum is σ = 207208032. Its totient is φ = 103604012.

The previous prime is 155406001. The next prime is 155406023. The reversal of 155406021 is 120604551.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 155406021 - 2⁵ = 155405989 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 155405982 and 155406000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155406023) 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 in 3 ways as a sum of consecutive naturals, for example, 25901001 + ... + 25901006.

It is an arithmetic number, because the mean of its divisors is an integer number (51802008).

Almost surely, 2^155406021 is an apocalyptic number.

It is an amenable number.

155406021 is a deficient number, since it is larger than the sum of its proper divisors (51802011).

155406021 is an equidigital number, since it uses as much as digits as its factorization.

155406021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 51802010.

The product of its (nonzero) digits is 1200, while the sum is 24.

The square root of 155406021 is about 12466.1951292285. The cubic root of 155406021 is about 537.6371624712.

The spelling of 155406021 in words is "one hundred fifty-five million, four hundred six thousand, twenty-one".