991522061 has 2 divisors, whose sum is σ = 991522062. Its totient is φ = 991522060.

The previous prime is 991522057. The next prime is 991522099. The reversal of 991522061 is 160225199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 763693225 + 227828836 = 27635^2 + 15094^2 .

It is a cyclic number.

It is not a de Polignac number, because 991522061 - 2² = 991522057 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (991522561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495761030 + 495761031.

It is an arithmetic number, because the mean of its divisors is an integer number (495761031).

Almost surely, 2^991522061 is an apocalyptic number.

It is an amenable number.

991522061 is a deficient number, since it is larger than the sum of its proper divisors (1).

991522061 is an equidigital number, since it uses as much as digits as its factorization.

991522061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9720, while the sum is 35.

The square root of 991522061 is about 31488.4432927384. The cubic root of 991522061 is about 997.1659963438.

The spelling of 991522061 in words is "nine hundred ninety-one million, five hundred twenty-two thousand, sixty-one".