20440991 has 4 divisors (see below), whose sum is σ = 20687352. Its totient is φ = 20194632.

The previous prime is 20440961. The next prime is 20440993. The reversal of 20440991 is 19904402.

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 20440991 - 2²² = 16246687 is a prime.

It is a super-2 number, since 2×20440991² = 835668226124162, 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 (20440993) 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, 123056 + ... + 123221.

It is an arithmetic number, because the mean of its divisors is an integer number (5171838).

Almost surely, 2^20440991 is an apocalyptic number.

20440991 is a deficient number, since it is larger than the sum of its proper divisors (246361).

20440991 is an equidigital number, since it uses as much as digits as its factorization.

20440991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 246360.

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 20440991 is about 4521.1714190019. The cubic root of 20440991 is about 273.4223315515.

The spelling of 20440991 in words is "twenty million, four hundred forty thousand, nine hundred ninety-one".