21868031 has 4 divisors (see below), whose sum is σ = 23019000. Its totient is φ = 20717064.

The previous prime is 21868013. The next prime is 21868039. The reversal of 21868031 is 13086812.

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 21868031 - 2¹⁸ = 21605887 is a prime.

It is a super-2 number, since 2×21868031² = 956421559633922, 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 = 21867985 and 21868003.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21868039) 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, 575456 + ... + 575493.

It is an arithmetic number, because the mean of its divisors is an integer number (5754750).

Almost surely, 2^21868031 is an apocalyptic number.

21868031 is a deficient number, since it is larger than the sum of its proper divisors (1150969).

21868031 is a wasteful number, since it uses less digits than its factorization.

21868031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1150968.

The product of its (nonzero) digits is 2304, while the sum is 29.

The square root of 21868031 is about 4676.3266566826. The cubic root of 21868031 is about 279.6425327726.

The spelling of 21868031 in words is "twenty-one million, eight hundred sixty-eight thousand, thirty-one".