15997981 has 8 divisors (see below), whose sum is σ = 16956000. Its totient is φ = 15051600.

The previous prime is 15997979. The next prime is 15997999. The reversal of 15997981 is 18979951.

It is a happy number.

15997981 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a cyclic number.

It is not a de Polignac number, because 15997981 - 2¹ = 15997979 is a prime.

It is a super-2 number, since 2×15997981² = 511870792152722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15997181) 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, 6 + ... + 5656.

It is an arithmetic number, because the mean of its divisors is an integer number (2119500).

Almost surely, 2^15997981 is an apocalyptic number.

It is an amenable number.

15997981 is a deficient number, since it is larger than the sum of its proper divisors (958019).

15997981 is a wasteful number, since it uses less digits than its factorization.

15997981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5819.

The product of its digits is 204120, while the sum is 49.

The square root of 15997981 is about 3999.7476170379. The cubic root of 15997981 is about 251.9736104473.

The spelling of 15997981 in words is "fifteen million, nine hundred ninety-seven thousand, nine hundred eighty-one".