645734661 has 16 divisors (see below), whose sum is σ = 1011501120. Its totient is φ = 361249920.

The previous prime is 645734659. The next prime is 645734717. The reversal of 645734661 is 166437546.

It is not a de Polignac number, because 645734661 - 2¹ = 645734659 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645734651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 752176 + ... + 753033.

It is an arithmetic number, because the mean of its divisors is an integer number (63218820).

Almost surely, 2^645734661 is an apocalyptic number.

It is an amenable number.

645734661 is a deficient number, since it is larger than the sum of its proper divisors (365766459).

645734661 is a wasteful number, since it uses less digits than its factorization.

645734661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1505236.

The product of its digits is 362880, while the sum is 42.

The square root of 645734661 is about 25411.3097065067. The cubic root of 645734661 is about 864.3401746370.

The spelling of 645734661 in words is "six hundred forty-five million, seven hundred thirty-four thousand, six hundred sixty-one".