20451 has 8 divisors (see below), whose sum is σ = 28944. Its totient is φ = 12800.
The previous prime is 20443. The next prime is 20477. The reversal of 20451 is 15402.
It is a sphenic number, since it is the product of 3 distinct primes.
It is a 9-Lehmer number, since φ(20451) divides (20451-1)9.
It is a cyclic number.
It is not a de Polignac number, because 20451 - 23 = 20443 is a prime.
It is not an unprimeable number, because it can be changed into a prime (20411) by changing a digit.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 150 + ... + 251.
It is an arithmetic number, because the mean of its divisors is an integer number (3618).
220451 is an apocalyptic number.
20451 is a deficient number, since it is larger than the sum of its proper divisors (8493).
20451 is a wasteful number, since it uses less digits than its factorization.
With its predecessor (20450) it forms a Ruth-Aaron pair, since the sum of their prime factors is the same (421).
20451 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 421.
The product of its (nonzero) digits is 40, while the sum is 12.
The square root of 20451 is about 143.0069928360. The cubic root of 20451 is about 27.3466951658.
Adding to 20451 its reverse (15402), we get a palindrome (35853).
It can be divided in two parts, 204 and 51, that multiplied together give a square (10404 = 1022).
The spelling of 20451 in words is "twenty thousand, four hundred fifty-one".
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