20724861 has 4 divisors (see below), whose sum is σ = 27633152. Its totient is φ = 13816572.

The previous prime is 20724841. The next prime is 20724889. The reversal of 20724861 is 16842702.

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 20724861 - 2⁶ = 20724797 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20724841) 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, 3454141 + ... + 3454146.

It is an arithmetic number, because the mean of its divisors is an integer number (6908288).

Almost surely, 2^20724861 is an apocalyptic number.

It is an amenable number.

20724861 is a deficient number, since it is larger than the sum of its proper divisors (6908291).

20724861 is an equidigital number, since it uses as much as digits as its factorization.

20724861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6908290.

The product of its (nonzero) digits is 5376, while the sum is 30.

The square root of 20724861 is about 4552.4565895789. The cubic root of 20724861 is about 274.6822158369.

The spelling of 20724861 in words is "twenty million, seven hundred twenty-four thousand, eight hundred sixty-one".