21125051 has 4 divisors (see below), whose sum is σ = 21265104. Its totient is φ = 20985000.

The previous prime is 21125029. The next prime is 21125057. The reversal of 21125051 is 15052112.

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 21125051 - 2¹⁴ = 21108667 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21125057) 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, 69800 + ... + 70101.

It is an arithmetic number, because the mean of its divisors is an integer number (5316276).

Almost surely, 2^21125051 is an apocalyptic number.

21125051 is a deficient number, since it is larger than the sum of its proper divisors (140053).

21125051 is a wasteful number, since it uses less digits than its factorization.

21125051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140052.

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

The square root of 21125051 is about 4596.1996257778. The cubic root of 21125051 is about 276.4389631433.

Adding to 21125051 its reverse (15052112), we get a palindrome (36177163).

The spelling of 21125051 in words is "twenty-one million, one hundred twenty-five thousand, fifty-one".