1491721779 has 16 divisors (see below), whose sum is σ = 1999388160. Its totient is φ = 989283360.

The previous prime is 1491721769. The next prime is 1491721783. The reversal of 1491721779 is 9771271941.

It is not a de Polignac number, because 1491721779 - 2⁵ = 1491721747 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1491721769) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 506092 + ... + 509030.

It is an arithmetic number, because the mean of its divisors is an integer number (124961760).

Almost surely, 2^1491721779 is an apocalyptic number.

1491721779 is a deficient number, since it is larger than the sum of its proper divisors (507666381).

1491721779 is a wasteful number, since it uses less digits than its factorization.

1491721779 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3770.

The product of its digits is 222264, while the sum is 48.

The square root of 1491721779 is about 38622.8142294163. The cubic root of 1491721779 is about 1142.6045350902.

The spelling of 1491721779 in words is "one billion, four hundred ninety-one million, seven hundred twenty-one thousand, seven hundred seventy-nine".