21097081 has 8 divisors (see below), whose sum is σ = 21832704. Its totient is φ = 20364960.

The previous prime is 21097057. The next prime is 21097091. The reversal of 21097081 is 18079012.

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 21097081 - 2⁷ = 21096953 is a prime.

It is a super-2 number, since 2×21097081² = 890173653441122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21097091) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18576 + ... + 19678.

It is an arithmetic number, because the mean of its divisors is an integer number (2729088).

Almost surely, 2^21097081 is an apocalyptic number.

It is an amenable number.

21097081 is a deficient number, since it is larger than the sum of its proper divisors (735623).

21097081 is a wasteful number, since it uses less digits than its factorization.

21097081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1751.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 21097081 is about 4593.1558867515. The cubic root of 21097081 is about 276.3169056431.

The spelling of 21097081 in words is "twenty-one million, ninety-seven thousand, eighty-one".