64190781 has 6 divisors (see below), whose sum is σ = 92720030. Its totient is φ = 42793848.

The previous prime is 64190779. The next prime is 64190807. The reversal of 64190781 is 18709146.

64190781 is a `hidden beast` number, since 641 + 9 + 0 + 7 + 8 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 49491225 + 14699556 = 7035^2 + 3834^2 .

It is not a de Polignac number, because 64190781 - 2¹ = 64190779 is a prime.

It is a super-2 number, since 2×64190781² = 8240912730779922, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64190681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3566146 + ... + 3566163.

Almost surely, 2^64190781 is an apocalyptic number.

It is an amenable number.

64190781 is a deficient number, since it is larger than the sum of its proper divisors (28529249).

64190781 is a wasteful number, since it uses less digits than its factorization.

64190781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7132315 (or 7132312 counting only the distinct ones).

The product of its (nonzero) digits is 12096, while the sum is 36.

The square root of 64190781 is about 8011.9149396383. The cubic root of 64190781 is about 400.3970661325.

It can be divided in two parts, 6 and 4190781, that multiplied together give a triangular number (25144686 = T₇₀₉₁).

The spelling of 64190781 in words is "sixty-four million, one hundred ninety thousand, seven hundred eighty-one".