155421 has 12 divisors (see below), whose sum is σ = 256672. Its totient is φ = 88776.

The previous prime is 155413. The next prime is 155423. The reversal of 155421 is 124551.

It is not a de Polignac number, because 155421 - 2³ = 155413 is a prime.

It is an Ulam number.

It is a Duffinian number.

155421 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 155394 and 155403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155423) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1171 + ... + 1296.

2¹⁵⁵⁴²¹ is an apocalyptic number.

It is an amenable number.

155421 is a deficient number, since it is larger than the sum of its proper divisors (101251).

155421 is a wasteful number, since it uses less digits than its factorization.

155421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2480 (or 2477 counting only the distinct ones).

The product of its digits is 200, while the sum is 18.

The square root of 155421 is about 394.2347016689. The cubic root of 155421 is about 53.7654435522.

Subtracting from 155421 its sum of digits (18), we obtain a triangular number (155403 = T₅₅₇).

Adding to 155421 its reverse (124551), we get a palindrome (279972).

It can be divided in two parts, 155 and 421, that added together give a square (576 = 24²).

The spelling of 155421 in words is "one hundred fifty-five thousand, four hundred twenty-one".