20721253 has 8 divisors (see below), whose sum is σ = 23764608. Its totient is φ = 17698704.

The previous prime is 20721223. The next prime is 20721263. The reversal of 20721253 is 35212702.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 20721253 - 2²¹ = 18624101 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721223) 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 7 ways as a sum of consecutive naturals, for example, 3001 + ... + 7102.

It is an arithmetic number, because the mean of its divisors is an integer number (2970576).

Almost surely, 2^20721253 is an apocalyptic number.

It is an amenable number.

20721253 is a deficient number, since it is larger than the sum of its proper divisors (3043355).

20721253 is a wasteful number, since it uses less digits than its factorization.

20721253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10403.

The product of its (nonzero) digits is 840, while the sum is 22.

The square root of 20721253 is about 4552.0603027640. The cubic root of 20721253 is about 274.6662750633. Note that the first 3 decimals are identical.

Adding to 20721253 its reverse (35212702), we get a palindrome (55933955).

The spelling of 20721253 in words is "twenty million, seven hundred twenty-one thousand, two hundred fifty-three".