20806997 has 4 divisors (see below), whose sum is σ = 22030956. Its totient is φ = 19583040.

The previous prime is 20806993. The next prime is 20807011. The reversal of 20806997 is 79960802.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 79960802 = 2 ⋅39980401.

It can be written as a sum of positive squares in 2 ways, for example, as 19061956 + 1745041 = 4366^2 + 1321^2 .

It is a cyclic number.

It is not a de Polignac number, because 20806997 - 2² = 20806993 is a prime.

It is a super-2 number, since 2×20806997² = 865862248316018, 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 (20806993) 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, 611954 + ... + 611987.

It is an arithmetic number, because the mean of its divisors is an integer number (5507739).

Almost surely, 2^20806997 is an apocalyptic number.

It is an amenable number.

20806997 is a deficient number, since it is larger than the sum of its proper divisors (1223959).

20806997 is a wasteful number, since it uses less digits than its factorization.

20806997 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1223958.

The product of its (nonzero) digits is 54432, while the sum is 41.

The square root of 20806997 is about 4561.4687327658. The cubic root of 20806997 is about 275.0446076399.

The spelling of 20806997 in words is "twenty million, eight hundred six thousand, nine hundred ninety-seven".