531240021 has 48 divisors (see below), whose sum is σ = 885109680. Its totient is φ = 304128000.

The previous prime is 531240011. The next prime is 531240023. The reversal of 531240021 is 120042135.

It can be written as a sum of positive squares in 8 ways, for example, as 19847025 + 511392996 = 4455^2 + 22614^2 .

It is not a de Polignac number, because 531240021 - 2²⁵ = 497685589 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 531239976 and 531240003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (531240023) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 175521 + ... + 178521.

It is an arithmetic number, because the mean of its divisors is an integer number (18439785).

Almost surely, 2^531240021 is an apocalyptic number.

531240021 is a gapful number since it is divisible by the number (51) formed by its first and last digit.

It is an amenable number.

531240021 is a deficient number, since it is larger than the sum of its proper divisors (353869659).

531240021 is a wasteful number, since it uses less digits than its factorization.

531240021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3126 (or 3123 counting only the distinct ones).

The product of its (nonzero) digits is 240, while the sum is 18.

The square root of 531240021 is about 23048.6446673118. The cubic root of 531240021 is about 809.8978792153.

Adding to 531240021 its reverse (120042135), we get a palindrome (651282156).

The spelling of 531240021 in words is "five hundred thirty-one million, two hundred forty thousand, twenty-one".