20798991 has 16 divisors (see below), whose sum is σ = 30912000. Its totient is φ = 13821624.

The previous prime is 20798989. The next prime is 20798993. The reversal of 20798991 is 19989702.

It is an interprime number because it is at equal distance from previous prime (20798989) and next prime (20798993).

It is not a de Polignac number, because 20798991 - 2¹ = 20798989 is a prime.

It is a Smith number, since the sum of its digits (45) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20798993) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8860 + ... + 10958.

It is an arithmetic number, because the mean of its divisors is an integer number (1932000).

Almost surely, 2^20798991 is an apocalyptic number.

20798991 is a deficient number, since it is larger than the sum of its proper divisors (10113009).

20798991 is a wasteful number, since it uses less digits than its factorization.

20798991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2475 (or 2469 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 20798991 is about 4560.5910801123. The cubic root of 20798991 is about 275.0093264055.

The spelling of 20798991 in words is "twenty million, seven hundred ninety-eight thousand, nine hundred ninety-one".