21670531 has 8 divisors (see below), whose sum is σ = 22659840. Its totient is φ = 20685192.

The previous prime is 21670513. The next prime is 21670543. The reversal of 21670531 is 13507612.

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 21670531 - 2⁷ = 21670403 is a prime.

It is a super-2 number, since 2×21670531² = 939223827643922, 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 = 21670496 and 21670505.

It is not an unprimeable number, because it can be changed into a prime (21670501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18736 + ... + 19858.

It is an arithmetic number, because the mean of its divisors is an integer number (2832480).

Almost surely, 2^21670531 is an apocalyptic number.

21670531 is a deficient number, since it is larger than the sum of its proper divisors (989309).

21670531 is a wasteful number, since it uses less digits than its factorization.

21670531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1985.

The product of its (nonzero) digits is 1260, while the sum is 25.

The square root of 21670531 is about 4655.1617587362. The cubic root of 21670531 is about 278.7981265145.

It can be divided in two parts, 21670 and 531, that added together give a square (22201 = 149²).

The spelling of 21670531 in words is "twenty-one million, six hundred seventy thousand, five hundred thirty-one".