20721252 has 48 divisors (see below), whose sum is σ = 50843520. Its totient is φ = 6555648.

The previous prime is 20721223. The next prime is 20721263. The reversal of 20721252 is 25212702.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 53074 + ... + 53462.

It is an arithmetic number, because the mean of its divisors is an integer number (1059240).

Almost surely, 2^20721252 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20721252, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25421760).

20721252 is an abundant number, since it is smaller than the sum of its proper divisors (30122268).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20721252 is a wasteful number, since it uses less digits than its factorization.

20721252 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 612 (or 610 counting only the distinct ones).

The product of its (nonzero) digits is 560, while the sum is 21.

The square root of 20721252 is about 4552.0601929236. The cubic root of 20721252 is about 274.6662706449. Note that the first 3 decimals are identical.

Adding to 20721252 its reverse (25212702), we get a palindrome (45933954).

The spelling of 20721252 in words is "twenty million, seven hundred twenty-one thousand, two hundred fifty-two".