21055051 has 4 divisors (see below), whose sum is σ = 21970512. Its totient is φ = 20139592.

The previous prime is 21055043. The next prime is 21055063. The reversal of 21055051 is 15055012.

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 21055051 - 2³ = 21055043 is a prime.

It is a super-2 number, since 2×21055051² = 886630345225202, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21055351) 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, 457696 + ... + 457741.

It is an arithmetic number, because the mean of its divisors is an integer number (5492628).

Almost surely, 2^21055051 is an apocalyptic number.

21055051 is a deficient number, since it is larger than the sum of its proper divisors (915461).

21055051 is an equidigital number, since it uses as much as digits as its factorization.

21055051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 915460.

The product of its (nonzero) digits is 250, while the sum is 19.

The square root of 21055051 is about 4588.5783201336. The cubic root of 21055051 is about 276.1332890823.

The spelling of 21055051 in words is "twenty-one million, fifty-five thousand, fifty-one".