1634663721 has 4 divisors (see below), whose sum is σ = 2179551632. Its totient is φ = 1089775812.

The previous prime is 1634663687. The next prime is 1634663729. The reversal of 1634663721 is 1273664361.

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 de Polignac number, because none of the positive numbers 2^k-1634663721 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1634663721.

It is not an unprimeable number, because it can be changed into a prime (1634663729) 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, 272443951 + ... + 272443956.

It is an arithmetic number, because the mean of its divisors is an integer number (544887908).

Almost surely, 2^1634663721 is an apocalyptic number.

It is an amenable number.

1634663721 is a deficient number, since it is larger than the sum of its proper divisors (544887911).

1634663721 is an equidigital number, since it uses as much as digits as its factorization.

1634663721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 544887910.

The product of its digits is 108864, while the sum is 39.

The square root of 1634663721 is about 40430.9747718256. The cubic root of 1634663721 is about 1177.9932666803.

The spelling of 1634663721 in words is "one billion, six hundred thirty-four million, six hundred sixty-three thousand, seven hundred twenty-one".