20691863 has 4 divisors (see below), whose sum is σ = 20807640. Its totient is φ = 20576088.

The previous prime is 20691859. The next prime is 20691887. The reversal of 20691863 is 36819602.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 36819602 = 2 ⋅18409801.

It is a cyclic number.

It is not a de Polignac number, because 20691863 - 2² = 20691859 is a prime.

It is a super-4 number, since 4×20691863⁴ (a number of 30 digits) contains 4444 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 (20691823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 57620 + ... + 57977.

It is an arithmetic number, because the mean of its divisors is an integer number (5201910).

Almost surely, 2^20691863 is an apocalyptic number.

20691863 is a deficient number, since it is larger than the sum of its proper divisors (115777).

20691863 is a wasteful number, since it uses less digits than its factorization.

20691863 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115776.

The product of its (nonzero) digits is 15552, while the sum is 35.

The square root of 20691863 is about 4548.8309487164. The cubic root of 20691863 is about 274.5363559355.

The spelling of 20691863 in words is "twenty million, six hundred ninety-one thousand, eight hundred sixty-three".