21593997 has 6 divisors (see below), whose sum is σ = 31191342. Its totient is φ = 14395992.

The previous prime is 21593983. The next prime is 21594019. The reversal of 21593997 is 79939512.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 13003236 + 8590761 = 3606^2 + 2931^2 .

It is not a de Polignac number, because 21593997 - 2¹¹ = 21591949 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21593917) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1199658 + ... + 1199675.

It is an arithmetic number, because the mean of its divisors is an integer number (5198557).

Almost surely, 2^21593997 is an apocalyptic number.

It is an amenable number.

21593997 is a deficient number, since it is larger than the sum of its proper divisors (9597345).

21593997 is a wasteful number, since it uses less digits than its factorization.

21593997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2399339 (or 2399336 counting only the distinct ones).

The product of its digits is 153090, while the sum is 45.

The square root of 21593997 is about 4646.9341505987. The cubic root of 21593997 is about 278.4695281284.

The spelling of 21593997 in words is "twenty-one million, five hundred ninety-three thousand, nine hundred ninety-seven".