16990721 has 8 divisors (see below), whose sum is σ = 19341504. Its totient is φ = 14774320.

The previous prime is 16990703. The next prime is 16990751. The reversal of 16990721 is 12709961.

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

It is not a de Polignac number, because 16990721 - 2⁶ = 16990657 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (16990751) 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, 33326 + ... + 33831.

It is an arithmetic number, because the mean of its divisors is an integer number (2417688).

Almost surely, 2^16990721 is an apocalyptic number.

16990721 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

16990721 is a deficient number, since it is larger than the sum of its proper divisors (2350783).

16990721 is a wasteful number, since it uses less digits than its factorization.

16990721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67191.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 16990721 is about 4121.9802279972. The cubic root of 16990721 is about 257.0813683519.

The spelling of 16990721 in words is "sixteen million, nine hundred ninety thousand, seven hundred twenty-one".