21590 has 16 divisors (see below), whose sum is σ = 41472. Its totient is φ = 8064.

The previous prime is 21589. The next prime is 21599. The reversal of 21590 is 9512.

21590 is an esthetic number in base 13 and base 16, because in such bases its adjacent digits differ by 1.

It is a super-2 number, since 2×21590² = 932256200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (17).

21590 is an undulating number in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21599) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 107 + ... + 233.

It is an arithmetic number, because the mean of its divisors is an integer number (2592).

2²¹⁵⁹⁰ is an apocalyptic number.

21590 is a deficient number, since it is larger than the sum of its proper divisors (19882).

21590 is a wasteful number, since it uses less digits than its factorization.

21590 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151.

The product of its (nonzero) digits is 90, while the sum is 17.

The square root of 21590 is about 146.9353599376. The cubic root of 21590 is about 27.8452345708.

The spelling of 21590 in words is "twenty-one thousand, five hundred ninety".