1971981649 has 15 divisors (see below), whose sum is σ = 2175092985. Its totient is φ = 1787825820.

The previous prime is 1971981629. The next prime is 1971981667. The reversal of 1971981649 is 9461891791.

The square root of 1971981649 is 44407.

It is a perfect power (a square), and thus also a powerful number.

It is not a de Polignac number, because 1971981649 - 2⁵ = 1971981617 is a prime.

It is a Duffinian number.

Its product of digits (979776) is a multiple of the sum of its prime divisors (378).

It is a self number, because there is not a number n which added to its sum of digits gives 1971981649.

It is not an unprimeable number, because it can be changed into a prime (1971981629) by changing a digit.

It is a polite number, since it can be written in 14 ways as a sum of consecutive naturals, for example, 5373064 + ... + 5373430.

It is an arithmetic number, because the mean of its divisors is an integer number (145006199).

Almost surely, 2^1971981649 is an apocalyptic number.

1971981649 is the 44407-th square number.

1971981649 is the 22204-th centered octagonal number.

It is an amenable number.

1971981649 is a deficient number, since it is larger than the sum of its proper divisors (203111336).

1971981649 is an frugal number, since it uses more digits than its factorization.

1971981649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 778 (or 378 counting only the distinct ones).

The product of its digits is 979776, while the sum is 55.

The cubic root of 1971981649 is about 1254.0098747555.

The spelling of 1971981649 in words is "one billion, nine hundred seventy-one million, nine hundred eighty-one thousand, six hundred forty-nine".