646761 has 4 divisors (see below), whose sum is σ = 862352. Its totient is φ = 431172.

The previous prime is 646757. The next prime is 646771. The reversal of 646761 is 167646.

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 646761 - 2² = 646757 is a prime.

It is a super-2 number, since 2×646761² = 836599582242, which contains 22 as substring.

It is a D-number.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (646721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 107791 + ... + 107796.

It is an arithmetic number, because the mean of its divisors is an integer number (215588).

2⁶⁴⁶⁷⁶¹ is an apocalyptic number.

It is an amenable number.

646761 is a deficient number, since it is larger than the sum of its proper divisors (215591).

646761 is a wasteful number, since it uses less digits than its factorization.

646761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215590.

The product of its digits is 6048, while the sum is 30.

The square root of 646761 is about 804.2145236192. The cubic root of 646761 is about 86.4797863378.

The spelling of 646761 in words is "six hundred forty-six thousand, seven hundred sixty-one".