646403561 has 2 divisors, whose sum is σ = 646403562. Its totient is φ = 646403560.

The previous prime is 646403557. The next prime is 646403603. The reversal of 646403561 is 165304646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 632824336 + 13579225 = 25156^2 + 3685^2 .

It is a cyclic number.

It is not a de Polignac number, because 646403561 - 2² = 646403557 is a prime.

It is not a weakly prime, because it can be changed into another prime (646403521) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323201780 + 323201781.

It is an arithmetic number, because the mean of its divisors is an integer number (323201781).

Almost surely, 2^646403561 is an apocalyptic number.

It is an amenable number.

646403561 is a deficient number, since it is larger than the sum of its proper divisors (1).

646403561 is an equidigital number, since it uses as much as digits as its factorization.

646403561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 51840, while the sum is 35.

The square root of 646403561 is about 25424.4677623741. The cubic root of 646403561 is about 864.6385209289.

The spelling of 646403561 in words is "six hundred forty-six million, four hundred three thousand, five hundred sixty-one".