21055031 has 4 divisors (see below), whose sum is σ = 21067200. Its totient is φ = 21042864.

The previous prime is 21055003. The next prime is 21055033. The reversal of 21055031 is 13055012.

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 21055031 - 2⁶ = 21054967 is a prime.

It is a super-2 number, since 2×21055031² = 886628660821922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21055033) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2951 + ... + 7128.

It is an arithmetic number, because the mean of its divisors is an integer number (5266800).

Almost surely, 2^21055031 is an apocalyptic number.

21055031 is a deficient number, since it is larger than the sum of its proper divisors (12169).

21055031 is a wasteful number, since it uses less digits than its factorization.

21055031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12168.

The product of its (nonzero) digits is 150, while the sum is 17.

The square root of 21055031 is about 4588.5761408088. The cubic root of 21055031 is about 276.1332016501.

The spelling of 21055031 in words is "twenty-one million, fifty-five thousand, thirty-one".