999978000521 has 2 divisors, whose sum is σ = 999978000522. Its totient is φ = 999978000520.

The previous prime is 999978000433. The next prime is 999978000529. The reversal of 999978000521 is 125000879999.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 999978000121 + 400 = 999989^2 + 20^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-999978000521 is a prime.

It is not a weakly prime, because it can be changed into another prime (999978000529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 499989000260 + 499989000261.

It is an arithmetic number, because the mean of its divisors is an integer number (499989000261).

Almost surely, 2^999978000521 is an apocalyptic number.

It is an amenable number.

999978000521 is a deficient number, since it is larger than the sum of its proper divisors (1).

999978000521 is an equidigital number, since it uses as much as digits as its factorization.

999978000521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3674160, while the sum is 59.

The spelling of 999978000521 in words is "nine hundred ninety-nine billion, nine hundred seventy-eight million, five hundred twenty-one", and thus it is an aban number.