21820031 has 8 divisors (see below), whose sum is σ = 22892544. Its totient is φ = 20757880.

The previous prime is 21820013. The next prime is 21820033. The reversal of 21820031 is 13002812.

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

It is not a de Polignac number, because 21820031 - 2¹⁴ = 21803647 is a prime.

It is a super-2 number, since 2×21820031² = 952227505681922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21819991 and 21820009.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21820033) 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, 1910 + ... + 6876.

It is an arithmetic number, because the mean of its divisors is an integer number (2861568).

Almost surely, 2^21820031 is an apocalyptic number.

21820031 is a deficient number, since it is larger than the sum of its proper divisors (1072513).

21820031 is a wasteful number, since it uses less digits than its factorization.

21820031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5181.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 21820031 is about 4671.1916038630. The cubic root of 21820031 is about 279.4377791676.

Adding to 21820031 its reverse (13002812), we get a palindrome (34822843).

The spelling of 21820031 in words is "twenty-one million, eight hundred twenty thousand, thirty-one".