1638491 has 4 divisors (see below), whose sum is σ = 1653912. Its totient is φ = 1623072.

The previous prime is 1638487. The next prime is 1638547. The reversal of 1638491 is 1948361.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1948361 = 41 ⋅47521.

It is a cyclic number.

It is not a de Polignac number, because 1638491 - 2² = 1638487 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1638431) 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, 7550 + ... + 7763.

It is an arithmetic number, because the mean of its divisors is an integer number (413478).

2^1638491 is an apocalyptic number.

1638491 is a deficient number, since it is larger than the sum of its proper divisors (15421).

1638491 is a wasteful number, since it uses less digits than its factorization.

1638491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15420.

The product of its digits is 5184, while the sum is 32.

The square root of 1638491 is about 1280.0355463814. The cubic root of 1638491 is about 117.8911905129.

The spelling of 1638491 in words is "one million, six hundred thirty-eight thousand, four hundred ninety-one".