20690 has 8 divisors (see below), whose sum is σ = 37260. Its totient is φ = 8272.

The previous prime is 20681. The next prime is 20693. The reversal of 20690 is 9602.

It can be written as a sum of positive squares in 2 ways, for example, as 19321 + 1369 = 139^2 + 37^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×20690² = 856152200, which contains 22 as substring.

It is an Ulam number.

It is a Curzon number.

It is a plaindrome in base 11 and base 14.

It is a nialpdrome in base 12.

It is not an unprimeable number, because it can be changed into a prime (20693) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1025 + ... + 1044.

2²⁰⁶⁹⁰ is an apocalyptic number.

20690 is a deficient number, since it is larger than the sum of its proper divisors (16570).

20690 is a wasteful number, since it uses less digits than its factorization.

20690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2076.

The product of its (nonzero) digits is 108, while the sum is 17.

The square root of 20690 is about 143.8401890989. The cubic root of 20690 is about 27.4528116359.

The spelling of 20690 in words is "twenty thousand, six hundred ninety".