640744421 has 8 divisors (see below), whose sum is σ = 644380800. Its totient is φ = 637116480.

The previous prime is 640744417. The next prime is 640744441. The reversal of 640744421 is 124447046.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 640744421 - 2² = 640744417 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (640744411) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 203741 + ... + 206861.

It is an arithmetic number, because the mean of its divisors is an integer number (80547600).

Almost surely, 2^640744421 is an apocalyptic number.

It is an amenable number.

640744421 is a deficient number, since it is larger than the sum of its proper divisors (3636379).

640744421 is a wasteful number, since it uses less digits than its factorization.

640744421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4219.

The product of its (nonzero) digits is 21504, while the sum is 32.

The square root of 640744421 is about 25312.9299173367. The cubic root of 640744421 is about 862.1078728880.

The spelling of 640744421 in words is "six hundred forty million, seven hundred forty-four thousand, four hundred twenty-one".