991964387 has 2 divisors, whose sum is σ = 991964388. Its totient is φ = 991964386.

The previous prime is 991964341. The next prime is 991964411. The reversal of 991964387 is 783469199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991964387 - 2¹⁰ = 991963363 is a prime.

It is not a weakly prime, because it can be changed into another prime (991964327) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495982193 + 495982194.

It is an arithmetic number, because the mean of its divisors is an integer number (495982194).

Almost surely, 2^991964387 is an apocalyptic number.

991964387 is a deficient number, since it is larger than the sum of its proper divisors (1).

991964387 is an equidigital number, since it uses as much as digits as its factorization.

991964387 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2939328, while the sum is 56.

The square root of 991964387 is about 31495.4661340327. The cubic root of 991964387 is about 997.3142555678.

The spelling of 991964387 in words is "nine hundred ninety-one million, nine hundred sixty-four thousand, three hundred eighty-seven".