64940781 has 4 divisors (see below), whose sum is σ = 86587712. Its totient is φ = 43293852.

The previous prime is 64940767. The next prime is 64940791. The reversal of 64940781 is 18704946.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 64940781 - 2⁶ = 64940717 is a prime.

It is a super-2 number, since 2×64940781² = 8434610073779922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (64940791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10823461 + ... + 10823466.

It is an arithmetic number, because the mean of its divisors is an integer number (21646928).

Almost surely, 2^64940781 is an apocalyptic number.

It is an amenable number.

64940781 is a deficient number, since it is larger than the sum of its proper divisors (21646931).

64940781 is a wasteful number, since it uses less digits than its factorization.

64940781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21646930.

The product of its (nonzero) digits is 48384, while the sum is 39.

The square root of 64940781 is about 8058.5843049508. The cubic root of 64940781 is about 401.9504344721.

The spelling of 64940781 in words is "sixty-four million, nine hundred forty thousand, seven hundred eighty-one".