20604991 has 4 divisors (see below), whose sum is σ = 22478184. Its totient is φ = 18731800.

The previous prime is 20604973. The next prime is 20605019. The reversal of 20604991 is 19940602.

It is a happy number.

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 20604991 - 2⁵ = 20604959 is a prime.

It is a super-2 number, since 2×20604991² = 849131308220162, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a pancake number, because a pancake can be divided into 20604991 parts by 6419 straight cuts.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20604931) 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, 936580 + ... + 936601.

It is an arithmetic number, because the mean of its divisors is an integer number (5619546).

Almost surely, 2^20604991 is an apocalyptic number.

20604991 is a deficient number, since it is larger than the sum of its proper divisors (1873193).

20604991 is a wasteful number, since it uses less digits than its factorization.

20604991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1873192.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 20604991 is about 4539.2720782081. The cubic root of 20604991 is about 274.1516157003.

The spelling of 20604991 in words is "twenty million, six hundred four thousand, nine hundred ninety-one".