20721743 has 12 divisors (see below), whose sum is σ = 24260688. Its totient is φ = 17337600.

The previous prime is 20721737. The next prime is 20721749. The reversal of 20721743 is 34712702.

It is an interprime number because it is at equal distance from previous prime (20721737) and next prime (20721749).

It is not a de Polignac number, because 20721743 - 2¹⁰ = 20720719 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 (20721749) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12143 + ... + 13743.

It is an arithmetic number, because the mean of its divisors is an integer number (2021724).

Almost surely, 2^20721743 is an apocalyptic number.

20721743 is a deficient number, since it is larger than the sum of its proper divisors (3538945).

20721743 is an equidigital number, since it uses as much as digits as its factorization.

20721743 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1694 (or 1651 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 26.

The square root of 20721743 is about 4552.1141242284. The cubic root of 20721743 is about 274.6684400774.

The spelling of 20721743 in words is "twenty million, seven hundred twenty-one thousand, seven hundred forty-three".