51215531 has 4 divisors (see below), whose sum is σ = 51264864. Its totient is φ = 51166200.

The previous prime is 51215501. The next prime is 51215551. The reversal of 51215531 is 13551215.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 51215531 - 2⁶ = 51215467 is a prime.

It is a super-2 number, since 2×51215531² = 5246061231223922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 51215497 and 51215506.

It is not an unprimeable number, because it can be changed into a prime (51215501) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 23075 + ... + 25196.

It is an arithmetic number, because the mean of its divisors is an integer number (12816216).

Almost surely, 2^51215531 is an apocalyptic number.

51215531 is a deficient number, since it is larger than the sum of its proper divisors (49333).

51215531 is a wasteful number, since it uses less digits than its factorization.

51215531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49332.

The product of its digits is 750, while the sum is 23.

The square root of 51215531 is about 7156.5027073285. The cubic root of 51215531 is about 371.3646489954.

Adding to 51215531 its reverse (13551215), we get a palindrome (64766746).

The spelling of 51215531 in words is "fifty-one million, two hundred fifteen thousand, five hundred thirty-one".