638137421 has 4 divisors (see below), whose sum is σ = 647125344. Its totient is φ = 629149500.

The previous prime is 638137361. The next prime is 638137433. The reversal of 638137421 is 124731836.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 638137421 - 2¹⁴ = 638121037 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 (638137441) 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, 4493855 + ... + 4493996.

It is an arithmetic number, because the mean of its divisors is an integer number (161781336).

Almost surely, 2^638137421 is an apocalyptic number.

It is an amenable number.

638137421 is a deficient number, since it is larger than the sum of its proper divisors (8987923).

638137421 is an equidigital number, since it uses as much as digits as its factorization.

638137421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8987922.

The product of its digits is 24192, while the sum is 35.

The square root of 638137421 is about 25261.3820089084. The cubic root of 638137421 is about 860.9370626979.

The spelling of 638137421 in words is "six hundred thirty-eight million, one hundred thirty-seven thousand, four hundred twenty-one".