21945031 has 4 divisors (see below), whose sum is σ = 21954832. Its totient is φ = 21935232.

The previous prime is 21945029. The next prime is 21945043. The reversal of 21945031 is 13054912.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21945031 - 2¹ = 21945029 is a prime.

It is a super-2 number, since 2×21945031² = 963168771181922, 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 = 21944987 and 21945005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21915031) 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, 295 + ... + 6631.

It is an arithmetic number, because the mean of its divisors is an integer number (5488708).

Almost surely, 2^21945031 is an apocalyptic number.

21945031 is a deficient number, since it is larger than the sum of its proper divisors (9801).

21945031 is an equidigital number, since it uses as much as digits as its factorization.

21945031 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9800.

The product of its (nonzero) digits is 1080, while the sum is 25.

The square root of 21945031 is about 4684.5523798971. The cubic root of 21945031 is about 279.9703667619.

Adding to 21945031 its reverse (13054912), we get a palindrome (34999943).

It can be divided in two parts, 2194 and 5031, that added together give a square (7225 = 85²).

The spelling of 21945031 in words is "twenty-one million, nine hundred forty-five thousand, thirty-one".