20998691 has 4 divisors (see below), whose sum is σ = 23998512. Its totient is φ = 17998872.

The previous prime is 20998673. The next prime is 20998727. The reversal of 20998691 is 19689902.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20998691 - 2¹⁴ = 20982307 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20998891) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1499900 + ... + 1499913.

It is an arithmetic number, because the mean of its divisors is an integer number (5999628).

Almost surely, 2^20998691 is an apocalyptic number.

20998691 is a deficient number, since it is larger than the sum of its proper divisors (2999821).

20998691 is an equidigital number, since it uses as much as digits as its factorization.

20998691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2999820.

The product of its (nonzero) digits is 69984, while the sum is 44.

The square root of 20998691 is about 4582.4328691209. The cubic root of 20998691 is about 275.8866850877.

The spelling of 20998691 in words is "twenty million, nine hundred ninety-eight thousand, six hundred ninety-one".