641628409 has 4 divisors (see below), whose sum is σ = 644885604. Its totient is φ = 638371216.

The previous prime is 641628373. The next prime is 641628469. The reversal of 641628409 is 904826146.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 546624400 + 95004009 = 23380^2 + 9747^2 .

It is a cyclic number.

It is not a de Polignac number, because 641628409 - 2²⁷ = 507410681 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641628469) 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, 1628302 + ... + 1628695.

It is an arithmetic number, because the mean of its divisors is an integer number (161221401).

Almost surely, 2^641628409 is an apocalyptic number.

It is an amenable number.

641628409 is a deficient number, since it is larger than the sum of its proper divisors (3257195).

641628409 is a wasteful number, since it uses less digits than its factorization.

641628409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3257194.

The product of its (nonzero) digits is 82944, while the sum is 40.

The square root of 641628409 is about 25330.3850937959. The cubic root of 641628409 is about 862.5041530011.

The spelling of 641628409 in words is "six hundred forty-one million, six hundred twenty-eight thousand, four hundred nine".