21597081 has 16 divisors (see below), whose sum is σ = 31518720. Its totient is φ = 13045520.

The previous prime is 21597071. The next prime is 21597113. The reversal of 21597081 is 18079512.

It is a cyclic number.

It is not a de Polignac number, because 21597081 - 2¹⁴ = 21580697 is a prime.

It is a super-2 number, since 2×21597081² = 932867815441122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21597001) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10936 + ... + 12758.

It is an arithmetic number, because the mean of its divisors is an integer number (1969920).

Almost surely, 2^21597081 is an apocalyptic number.

It is an amenable number.

21597081 is a deficient number, since it is larger than the sum of its proper divisors (9921639).

21597081 is a wasteful number, since it uses less digits than its factorization.

21597081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2196.

The product of its (nonzero) digits is 5040, while the sum is 33.

The square root of 21597081 is about 4647.2659704390. The cubic root of 21597081 is about 278.4827842685.

The spelling of 21597081 in words is "twenty-one million, five hundred ninety-seven thousand, eighty-one".