21001597 has 16 divisors (see below), whose sum is σ = 22464000. Its totient is φ = 19603584.

The previous prime is 21001577. The next prime is 21001627. The reversal of 21001597 is 79510012.

It is a cyclic number.

It is not a de Polignac number, because 21001597 - 2⁷ = 21001469 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001577) 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 15 ways as a sum of consecutive naturals, for example, 203848 + ... + 203950.

It is an arithmetic number, because the mean of its divisors is an integer number (1404000).

Almost surely, 2^21001597 is an apocalyptic number.

It is an amenable number.

21001597 is a deficient number, since it is larger than the sum of its proper divisors (1462403).

21001597 is a wasteful number, since it uses less digits than its factorization.

21001597 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300.

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 21001597 is about 4582.7499386286. The cubic root of 21001597 is about 275.8994111147.

The spelling of 21001597 in words is "twenty-one million, one thousand, five hundred ninety-seven".