991658407 has 2 divisors, whose sum is σ = 991658408. Its totient is φ = 991658406.

The previous prime is 991658383. The next prime is 991658413. The reversal of 991658407 is 704856199.

It is a strong prime.

It is an emirp because it is prime and its reverse (704856199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991658407 - 2¹⁵ = 991625639 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991158407) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495829203 + 495829204.

It is an arithmetic number, because the mean of its divisors is an integer number (495829204).

Almost surely, 2^991658407 is an apocalyptic number.

991658407 is a deficient number, since it is larger than the sum of its proper divisors (1).

991658407 is an equidigital number, since it uses as much as digits as its factorization.

991658407 is an evil number, because the sum of its binary digits is even.

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

The square root of 991658407 is about 31490.6082348373. The cubic root of 991658407 is about 997.2117016181.

The spelling of 991658407 in words is "nine hundred ninety-one million, six hundred fifty-eight thousand, four hundred seven".