20721456 has 120 divisors (see below), whose sum is σ = 67562144. Its totient is φ = 5806080.

The previous prime is 20721439. The next prime is 20721461. The reversal of 20721456 is 65412702.

20721456 is a `hidden beast` number, since 207 + 2 + 1 + 456 = 666.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 61320 + ... + 61656.

Almost surely, 2^20721456 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 20721456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33781072).

20721456 is an abundant number, since it is smaller than the sum of its proper divisors (46840688).

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

20721456 is a wasteful number, since it uses less digits than its factorization.

20721456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 419 (or 410 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 27.

The square root of 20721456 is about 4552.0826003051. The cubic root of 20721456 is about 274.6671720019.

The spelling of 20721456 in words is "twenty million, seven hundred twenty-one thousand, four hundred fifty-six".