21251051 has 4 divisors (see below), whose sum is σ = 21470232. Its totient is φ = 21031872.

The previous prime is 21251023. The next prime is 21251053. The reversal of 21251051 is 15015212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21251051 - 2¹⁴ = 21234667 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21251053) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 109445 + ... + 109638.

It is an arithmetic number, because the mean of its divisors is an integer number (5367558).

Almost surely, 2^21251051 is an apocalyptic number.

21251051 is a deficient number, since it is larger than the sum of its proper divisors (219181).

21251051 is an equidigital number, since it uses as much as digits as its factorization.

21251051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219180.

The product of its (nonzero) digits is 100, while the sum is 17.

The square root of 21251051 is about 4609.8862241925. The cubic root of 21251051 is about 276.9874791788.

Adding to 21251051 its reverse (15015212), we get a palindrome (36266263).

The spelling of 21251051 in words is "twenty-one million, two hundred fifty-one thousand, fifty-one".