21155051 has 4 divisors (see below), whose sum is σ = 21837504. Its totient is φ = 20472600.

The previous prime is 21155041. The next prime is 21155053. The reversal of 21155051 is 15055112.

It is a happy number.

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 21155051 - 2¹⁰ = 21154027 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21155053) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 341180 + ... + 341241.

It is an arithmetic number, because the mean of its divisors is an integer number (5459376).

Almost surely, 2^21155051 is an apocalyptic number.

21155051 is a deficient number, since it is larger than the sum of its proper divisors (682453).

21155051 is an equidigital number, since it uses as much as digits as its factorization.

21155051 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 682452.

The product of its (nonzero) digits is 250, while the sum is 20.

The square root of 21155051 is about 4599.4620337600. The cubic root of 21155051 is about 276.5697596124.

The spelling of 21155051 in words is "twenty-one million, one hundred fifty-five thousand, fifty-one".