15978921 has 8 divisors (see below), whose sum is σ = 24348864. Its totient is φ = 9130800.

The previous prime is 15978899. The next prime is 15978923. The reversal of 15978921 is 12987951.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 15978921 - 2¹³ = 15970729 is a prime.

It is not an unprimeable number, because it can be changed into a prime (15978923) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 380430 + ... + 380471.

It is an arithmetic number, because the mean of its divisors is an integer number (3043608).

Almost surely, 2^15978921 is an apocalyptic number.

It is an amenable number.

15978921 is a deficient number, since it is larger than the sum of its proper divisors (8369943).

15978921 is an equidigital number, since it uses as much as digits as its factorization.

15978921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 760911.

The product of its digits is 45360, while the sum is 42.

The square root of 15978921 is about 3997.3642566071. The cubic root of 15978921 is about 251.8735035326.

The spelling of 15978921 in words is "fifteen million, nine hundred seventy-eight thousand, nine hundred twenty-one".