21064251 has 24 divisors (see below), whose sum is σ = 31649296. Its totient is φ = 12386880.

The previous prime is 21064249. The next prime is 21064259. The reversal of 21064251 is 15246012.

It is not a de Polignac number, because 21064251 - 2¹ = 21064249 is a prime.

It is a Smith number, since the sum of its digits (21) coincides with the sum of the digits of its prime factors.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21064259) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 20121 + ... + 21141.

Almost surely, 2^21064251 is an apocalyptic number.

21064251 is a deficient number, since it is larger than the sum of its proper divisors (10585045).

21064251 is a wasteful number, since it uses less digits than its factorization.

21064251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1083 (or 1060 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 21.

The square root of 21064251 is about 4589.5806998025. The cubic root of 21064251 is about 276.1735020196.

The spelling of 21064251 in words is "twenty-one million, sixty-four thousand, two hundred fifty-one".