646437681 has 12 divisors (see below), whose sum is σ = 934182340. Its totient is φ = 430755840.

The previous prime is 646437677. The next prime is 646437683. The reversal of 646437681 is 186734646.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 386712225 + 259725456 = 19665^2 + 16116^2 .

It is not a de Polignac number, because 646437681 - 2² = 646437677 is a prime.

It is a super-2 number, since 2×646437681² = 835763350833315522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (646437683) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4785 + ... + 36273.

Almost surely, 2^646437681 is an apocalyptic number.

It is an amenable number.

646437681 is a deficient number, since it is larger than the sum of its proper divisors (287744659).

646437681 is a wasteful number, since it uses less digits than its factorization.

646437681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33776 (or 33773 counting only the distinct ones).

The product of its digits is 580608, while the sum is 45.

The square root of 646437681 is about 25425.1387606833. The cubic root of 646437681 is about 864.6537337923.

The spelling of 646437681 in words is "six hundred forty-six million, four hundred thirty-seven thousand, six hundred eighty-one".