20432721 has 4 divisors (see below), whose sum is σ = 27243632. Its totient is φ = 13621812.

The previous prime is 20432707. The next prime is 20432729. The reversal of 20432721 is 12723402.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 20432721 - 2¹⁹ = 19908433 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (20432729) 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, 3405451 + ... + 3405456.

It is an arithmetic number, because the mean of its divisors is an integer number (6810908).

Almost surely, 2^20432721 is an apocalyptic number.

It is an amenable number.

20432721 is a deficient number, since it is larger than the sum of its proper divisors (6810911).

20432721 is an equidigital number, since it uses as much as digits as its factorization.

20432721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6810910.

The product of its (nonzero) digits is 672, while the sum is 21.

The square root of 20432721 is about 4520.2567404961. The cubic root of 20432721 is about 273.3854529139.

The spelling of 20432721 in words is "twenty million, four hundred thirty-two thousand, seven hundred twenty-one".