15978729649 has 9 divisors (see below), whose sum is σ = 16866513003. Its totient is φ = 15135468552.

The previous prime is 15978729629. The next prime is 15978729653. The reversal of 15978729649 is 94692787951.

It is a happy number.

The square root of 15978729649 is 126407.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 386712225 + 15592017424 = 19665^2 + 124868^2 .

It is not a de Polignac number, because 15978729649 - 2⁵ = 15978729617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (15978729629) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 2398407 + ... + 2405059.

Almost surely, 2^15978729649 is an apocalyptic number.

15978729649 is a gapful number since it is divisible by the number (19) formed by its first and last digit.

15978729649 is the 126407-th square number.

15978729649 is the 63204-th centered octagonal number.

It is an amenable number.

15978729649 is a deficient number, since it is larger than the sum of its proper divisors (887783354).

15978729649 is an frugal number, since it uses more digits than its factorization.

15978729649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13344 (or 6672 counting only the distinct ones).

The product of its digits is 68584320, while the sum is 67.

The spelling of 15978729649 in words is "fifteen billion, nine hundred seventy-eight million, seven hundred twenty-nine thousand, six hundred forty-nine".