20721285 has 32 divisors (see below), whose sum is σ = 39674880. Its totient is φ = 10200384.

The previous prime is 20721271. The next prime is 20721287. The reversal of 20721285 is 58212702.

It is not a de Polignac number, because 20721285 - 2¹⁰ = 20720261 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20721287) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4149 + ... + 7658.

It is an arithmetic number, because the mean of its divisors is an integer number (1239840).

Almost surely, 2^20721285 is an apocalyptic number.

It is an amenable number.

20721285 is a deficient number, since it is larger than the sum of its proper divisors (18953595).

20721285 is a wasteful number, since it uses less digits than its factorization.

20721285 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11834 (or 11828 counting only the distinct ones).

The product of its (nonzero) digits is 2240, while the sum is 27.

The square root of 20721285 is about 4552.0638176546. The cubic root of 20721285 is about 274.6664164530. Note that the first 3 decimals are identical.

Adding to 20721285 its reverse (58212702), we get a palindrome (78933987).

The spelling of 20721285 in words is "twenty million, seven hundred twenty-one thousand, two hundred eighty-five".