155725421 has 4 divisors (see below), whose sum is σ = 159523644. Its totient is φ = 151927200.

The previous prime is 155725411. The next prime is 155725499. The reversal of 155725421 is 124527551.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 124527551 = 257 ⋅484543.

It can be written as a sum of positive squares in 2 ways, for example, as 11485321 + 144240100 = 3389^2 + 12010^2 .

It is a cyclic number.

It is not a de Polignac number, because 155725421 - 2¹⁰ = 155724397 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155725411) 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, 1899050 + ... + 1899131.

It is an arithmetic number, because the mean of its divisors is an integer number (39880911).

Almost surely, 2^155725421 is an apocalyptic number.

It is an amenable number.

155725421 is a deficient number, since it is larger than the sum of its proper divisors (3798223).

155725421 is an equidigital number, since it uses as much as digits as its factorization.

155725421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3798222.

The product of its digits is 14000, while the sum is 32.

The square root of 155725421 is about 12478.9991986537. Note that the first 3 decimals coincide. The cubic root of 155725421 is about 538.0052387286.

The spelling of 155725421 in words is "one hundred fifty-five million, seven hundred twenty-five thousand, four hundred twenty-one".