1989435721 has 72 divisors (see below), whose sum is σ = 2650976064. Its totient is φ = 1485993600.

The previous prime is 1989435713. The next prime is 1989435733. The reversal of 1989435721 is 1275349891.

It is a happy number.

It is not a de Polignac number, because 1989435721 - 2³ = 1989435713 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (49).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1989435781) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 13174996 + ... + 13175146.

It is an arithmetic number, because the mean of its divisors is an integer number (36819112).

Almost surely, 2^1989435721 is an apocalyptic number.

It is an amenable number.

1989435721 is a deficient number, since it is larger than the sum of its proper divisors (661540343).

1989435721 is a wasteful number, since it uses less digits than its factorization.

1989435721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271 (or 251 counting only the distinct ones).

The product of its digits is 544320, while the sum is 49.

The square root of 1989435721 is about 44603.0909354946. The cubic root of 1989435721 is about 1257.6987729160.

The spelling of 1989435721 in words is "one billion, nine hundred eighty-nine million, four hundred thirty-five thousand, seven hundred twenty-one".