20721429 has 6 divisors (see below), whose sum is σ = 29930966. Its totient is φ = 13814280.

The previous prime is 20721401. The next prime is 20721433. The reversal of 20721429 is 92412702.

It can be written as a sum of positive squares in only one way, i.e., 16184529 + 4536900 = 4023^2 + 2130^2 .

It is not a de Polignac number, because 20721429 - 2⁵ = 20721397 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 (20721439) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1151182 + ... + 1151199.

Almost surely, 2^20721429 is an apocalyptic number.

It is an amenable number.

20721429 is a deficient number, since it is larger than the sum of its proper divisors (9209537).

20721429 is a wasteful number, since it uses less digits than its factorization.

20721429 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2302387 (or 2302384 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 20721429 is about 4552.0796346286. The cubic root of 20721429 is about 274.6670527050.

The spelling of 20721429 in words is "twenty million, seven hundred twenty-one thousand, four hundred twenty-nine".