20724661 has 4 divisors (see below), whose sum is σ = 20738272. Its totient is φ = 20711052.

The previous prime is 20724659. The next prime is 20724673. The reversal of 20724661 is 16642702.

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 a cyclic number.

It is not a de Polignac number, because 20724661 - 2¹ = 20724659 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 (20724601) 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, 4185 + ... + 7678.

It is an arithmetic number, because the mean of its divisors is an integer number (5184568).

Almost surely, 2^20724661 is an apocalyptic number.

It is an amenable number.

20724661 is a deficient number, since it is larger than the sum of its proper divisors (13611).

20724661 is a wasteful number, since it uses less digits than its factorization.

20724661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13610.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 20724661 is about 4552.4346233636. The cubic root of 20724661 is about 274.6813322505.

The spelling of 20724661 in words is "twenty million, seven hundred twenty-four thousand, six hundred sixty-one".