991213649 has 4 divisors (see below), whose sum is σ = 1025393460. Its totient is φ = 957033840.

The previous prime is 991213633. The next prime is 991213651. The reversal of 991213649 is 946312199.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 823977025 + 167236624 = 28705^2 + 12932^2 .

It is a cyclic number.

It is not a de Polignac number, because 991213649 - 2⁴ = 991213633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991213549) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17089862 + ... + 17089919.

It is an arithmetic number, because the mean of its divisors is an integer number (256348365).

Almost surely, 2^991213649 is an apocalyptic number.

It is an amenable number.

991213649 is a deficient number, since it is larger than the sum of its proper divisors (34179811).

991213649 is a wasteful number, since it uses less digits than its factorization.

991213649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34179810.

The product of its digits is 104976, while the sum is 44.

The square root of 991213649 is about 31483.5456865964. The cubic root of 991213649 is about 997.0625964420.

The spelling of 991213649 in words is "nine hundred ninety-one million, two hundred thirteen thousand, six hundred forty-nine".