643537651 has 2 divisors, whose sum is σ = 643537652. Its totient is φ = 643537650.

The previous prime is 643537639. The next prime is 643537663. The reversal of 643537651 is 156735346.

It is a balanced prime because it is at equal distance from previous prime (643537639) and next prime (643537663).

It is a cyclic number.

It is not a de Polignac number, because 643537651 - 2¹⁹ = 643013363 is a prime.

It is not a weakly prime, because it can be changed into another prime (643537621) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321768825 + 321768826.

It is an arithmetic number, because the mean of its divisors is an integer number (321768826).

Almost surely, 2^643537651 is an apocalyptic number.

643537651 is a deficient number, since it is larger than the sum of its proper divisors (1).

643537651 is an equidigital number, since it uses as much as digits as its factorization.

643537651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 226800, while the sum is 40.

The square root of 643537651 is about 25368.0438938441. The cubic root of 643537651 is about 863.3588005818.

The spelling of 643537651 in words is "six hundred forty-three million, five hundred thirty-seven thousand, six hundred fifty-one".