21084251 has 8 divisors (see below), whose sum is σ = 21337344. Its totient is φ = 20833000.

The previous prime is 21084227. The next prime is 21084253. The reversal of 21084251 is 15248012.

21084251 = T₁ + T₂ + ... + T₅₀₁.

21084251 is a nontrivial binomial coefficient, being equal to C(503, 3).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21084251 - 2⁶ = 21084187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21084253) by changing a digit.

It is the 501-st tetrahedral number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 41666 + ... + 42168.

It is an arithmetic number, because the mean of its divisors is an integer number (2667168).

Almost surely, 2^21084251 is an apocalyptic number.

21084251 is a deficient number, since it is larger than the sum of its proper divisors (253093).

21084251 is a wasteful number, since it uses less digits than its factorization.

21084251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 921.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21084251 is about 4591.7590311339. The cubic root of 21084251 is about 276.2608810712.

The spelling of 21084251 in words is "twenty-one million, eighty-four thousand, two hundred fifty-one".