64723781 has 2 divisors, whose sum is σ = 64723782. Its totient is φ = 64723780.

The previous prime is 64723739. The next prime is 64723783. The reversal of 64723781 is 18732746.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 60062500 + 4661281 = 7750^2 + 2159^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-64723781 is a prime.

It is a super-2 number, since 2×64723781² = 8378335653871922, which contains 22 as substring.

Together with 64723783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (64723783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 32361890 + 32361891.

It is an arithmetic number, because the mean of its divisors is an integer number (32361891).

Almost surely, 2^64723781 is an apocalyptic number.

It is an amenable number.

64723781 is a deficient number, since it is larger than the sum of its proper divisors (1).

64723781 is an equidigital number, since it uses as much as digits as its factorization.

64723781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 56448, while the sum is 38.

The square root of 64723781 is about 8045.1091353691. The cubic root of 64723781 is about 401.5022282961.

The spelling of 64723781 in words is "sixty-four million, seven hundred twenty-three thousand, seven hundred eighty-one".