1991224971 has 16 divisors (see below), whose sum is σ = 2977031200. Its totient is φ = 1315302624.

The previous prime is 1991224969. The next prime is 1991224979. The reversal of 1991224971 is 1794221991.

It is a happy number.

It is not a de Polignac number, because 1991224971 - 2¹ = 1991224969 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991224979) 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, 335356 + ... + 341241.

It is an arithmetic number, because the mean of its divisors is an integer number (186064450).

Almost surely, 2^1991224971 is an apocalyptic number.

1991224971 is a deficient number, since it is larger than the sum of its proper divisors (985806229).

1991224971 is a wasteful number, since it uses less digits than its factorization.

1991224971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 676715 (or 676709 counting only the distinct ones).

The product of its digits is 81648, while the sum is 45.

The square root of 1991224971 is about 44623.1438941722. The cubic root of 1991224971 is about 1258.0757078109.

The spelling of 1991224971 in words is "one billion, nine hundred ninety-one million, two hundred twenty-four thousand, nine hundred seventy-one".