15978649 has 2 divisors, whose sum is σ = 15978650. Its totient is φ = 15978648.

The previous prime is 15978617. The next prime is 15978673. The reversal of 15978649 is 94687951.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14768649 + 1210000 = 3843^2 + 1100^2 .

It is a cyclic number.

It is not a de Polignac number, because 15978649 - 2⁵ = 15978617 is a prime.

It is not a weakly prime, because it can be changed into another prime (15978679) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 7989324 + 7989325.

It is an arithmetic number, because the mean of its divisors is an integer number (7989325).

Almost surely, 2^15978649 is an apocalyptic number.

It is an amenable number.

15978649 is a deficient number, since it is larger than the sum of its proper divisors (1).

15978649 is an equidigital number, since it uses as much as digits as its factorization.

15978649 is an odious number, because the sum of its binary digits is odd.

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

The square root of 15978649 is about 3997.3302340437. The cubic root of 15978649 is about 251.8720743584.

The spelling of 15978649 in words is "fifteen million, nine hundred seventy-eight thousand, six hundred forty-nine".