21055431 has 8 divisors (see below), whose sum is σ = 28534384. Its totient is φ = 13806720.

The previous prime is 21055429. The next prime is 21055451. The reversal of 21055431 is 13455012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21055431 - 2¹ = 21055429 is a prime.

It is a super-2 number, since 2×21055431² = 886662349191522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21055398 and 21055407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21055451) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 57346 + ... + 57711.

It is an arithmetic number, because the mean of its divisors is an integer number (3566798).

Almost surely, 2^21055431 is an apocalyptic number.

21055431 is a deficient number, since it is larger than the sum of its proper divisors (7478953).

21055431 is a wasteful number, since it uses less digits than its factorization.

21055431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115121.

The product of its (nonzero) digits is 600, while the sum is 21.

The square root of 21055431 is about 4588.6197271075. The cubic root of 21055431 is about 276.1349502834.

The spelling of 21055431 in words is "twenty-one million, fifty-five thousand, four hundred thirty-one".