641902609 has 4 divisors (see below), whose sum is σ = 679661604. Its totient is φ = 604143616.

The previous prime is 641902589. The next prime is 641902619. The reversal of 641902609 is 906209146.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 906209146 = 2 ⋅453104573.

It can be written as a sum of positive squares in 2 ways, for example, as 206554384 + 435348225 = 14372^2 + 20865^2 .

It is a cyclic number.

It is not a de Polignac number, because 641902609 - 2¹³ = 641894417 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641902619) 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, 18879472 + ... + 18879505.

It is an arithmetic number, because the mean of its divisors is an integer number (169915401).

Almost surely, 2^641902609 is an apocalyptic number.

It is an amenable number.

641902609 is a deficient number, since it is larger than the sum of its proper divisors (37758995).

641902609 is a wasteful number, since it uses less digits than its factorization.

641902609 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37758994.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 641902609 is about 25335.7969876615. The cubic root of 641902609 is about 862.6269992644.

The spelling of 641902609 in words is "six hundred forty-one million, nine hundred two thousand, six hundred nine".