51213781 has 2 divisors, whose sum is σ = 51213782. Its totient is φ = 51213780.

The previous prime is 51213761. The next prime is 51213787. The reversal of 51213781 is 18731215.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 37271025 + 13942756 = 6105^2 + 3734^2 .

It is a cyclic number.

It is not a de Polignac number, because 51213781 - 2⁷ = 51213653 is a prime.

It is a super-2 number, since 2×51213781² = 5245702728631922, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (51213787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 25606890 + 25606891.

It is an arithmetic number, because the mean of its divisors is an integer number (25606891).

Almost surely, 2^51213781 is an apocalyptic number.

It is an amenable number.

51213781 is a deficient number, since it is larger than the sum of its proper divisors (1).

51213781 is an equidigital number, since it uses as much as digits as its factorization.

51213781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1680, while the sum is 28.

The square root of 51213781 is about 7156.3804398592. The cubic root of 51213781 is about 371.3604191878.

Adding to 51213781 its reverse (18731215), we get a palindrome (69944996).

The spelling of 51213781 in words is "fifty-one million, two hundred thirteen thousand, seven hundred eighty-one".