64851781 has 2 divisors, whose sum is σ = 64851782. Its totient is φ = 64851780.

The previous prime is 64851767. The next prime is 64851799. The reversal of 64851781 is 18715846.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 64480900 + 370881 = 8030^2 + 609^2 .

It is a cyclic number.

It is not a de Polignac number, because 64851781 - 2¹⁹ = 64327493 is a prime.

It is a super-2 number, since 2×64851781² = 8411506997743922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64851751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32425890 + 32425891.

It is an arithmetic number, because the mean of its divisors is an integer number (32425891).

Almost surely, 2^64851781 is an apocalyptic number.

It is an amenable number.

64851781 is a deficient number, since it is larger than the sum of its proper divisors (1).

64851781 is an equidigital number, since it uses as much as digits as its factorization.

64851781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 53760, while the sum is 40.

The square root of 64851781 is about 8053.0603499539. The cubic root of 64851781 is about 401.7667289336.

The spelling of 64851781 in words is "sixty-four million, eight hundred fifty-one thousand, seven hundred eighty-one".