1971721980 has 96 divisors (see below), whose sum is σ = 6283932480. Its totient is φ = 512962560.

The previous prime is 1971721963. The next prime is 1971721981. The reversal of 1971721980 is 891271791.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1971721981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 22389 + ... + 66668.

It is an arithmetic number, because the mean of its divisors is an integer number (65457630).

Almost surely, 2^1971721980 is an apocalyptic number.

1971721980 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1971721980 is an abundant number, since it is smaller than the sum of its proper divisors (4312210500).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1971721980 is a wasteful number, since it uses less digits than its factorization.

1971721980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 89116 (or 89108 counting only the distinct ones).

The product of its (nonzero) digits is 63504, while the sum is 45.

The square root of 1971721980 is about 44404.0761642442. The cubic root of 1971721980 is about 1253.9548299931.

The spelling of 1971721980 in words is "one billion, nine hundred seventy-one million, seven hundred twenty-one thousand, nine hundred eighty".