641640949 has 4 divisors (see below), whose sum is σ = 653747436. Its totient is φ = 629534464.

The previous prime is 641640943. The next prime is 641640953. The reversal of 641640949 is 949046146.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 949046146 = 2 ⋅474523073.

It can be written as a sum of positive squares in 2 ways, for example, as 417180625 + 224460324 = 20425^2 + 14982^2 .

It is a cyclic number.

It is not a de Polignac number, because 641640949 - 2¹⁵ = 641608181 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (641640943) 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, 6053164 + ... + 6053269.

It is an arithmetic number, because the mean of its divisors is an integer number (163436859).

Almost surely, 2^641640949 is an apocalyptic number.

It is an amenable number.

641640949 is a deficient number, since it is larger than the sum of its proper divisors (12106487).

641640949 is a wasteful number, since it uses less digits than its factorization.

641640949 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12106486.

The product of its (nonzero) digits is 186624, while the sum is 43.

The square root of 641640949 is about 25330.6326213934. The cubic root of 641640949 is about 862.5097718980.

The spelling of 641640949 in words is "six hundred forty-one million, six hundred forty thousand, nine hundred forty-nine".