51216781 has 8 divisors (see below), whose sum is σ = 63854784. Its totient is φ = 39909120.

The previous prime is 51216757. The next prime is 51216833. The reversal of 51216781 is 18761215.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 51216781 - 2¹³ = 51208589 is a prime.

It is a super-2 number, since 2×51216781² = 5246317312003922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (51216751) 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 7 ways as a sum of consecutive naturals, for example, 332500 + ... + 332653.

It is an arithmetic number, because the mean of its divisors is an integer number (7981848).

Almost surely, 2^51216781 is an apocalyptic number.

It is an amenable number.

51216781 is a deficient number, since it is larger than the sum of its proper divisors (12638003).

51216781 is a wasteful number, since it uses less digits than its factorization.

51216781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 665171.

The product of its digits is 3360, while the sum is 31.

The square root of 51216781 is about 7156.5900399562. The cubic root of 51216781 is about 371.3676702276.

Adding to 51216781 its reverse (18761215), we get a palindrome (69977996).

The spelling of 51216781 in words is "fifty-one million, two hundred sixteen thousand, seven hundred eighty-one".