21870031 has 8 divisors (see below), whose sum is σ = 22680720. Its totient is φ = 21063168.

The previous prime is 21870029. The next prime is 21870047. The reversal of 21870031 is 13007812.

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

It is a cyclic number.

It is not a de Polignac number, because 21870031 - 2¹ = 21870029 is a prime.

It is a super-2 number, since 2×21870031² = 956596511881922, 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 = 21869984 and 21870011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21870011) 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, 16080 + ... + 17386.

It is an arithmetic number, because the mean of its divisors is an integer number (2835090).

Almost surely, 2^21870031 is an apocalyptic number.

21870031 is a deficient number, since it is larger than the sum of its proper divisors (810689).

21870031 is a wasteful number, since it uses less digits than its factorization.

21870031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1913.

The product of its (nonzero) digits is 336, while the sum is 22.

The square root of 21870031 is about 4676.5404948530. The cubic root of 21870031 is about 279.6510576678.

Adding to 21870031 its reverse (13007812), we get a palindrome (34877843).

The spelling of 21870031 in words is "twenty-one million, eight hundred seventy thousand, thirty-one".