21690663 has 4 divisors (see below), whose sum is σ = 28920888. Its totient is φ = 14460440.

The previous prime is 21690653. The next prime is 21690703. The reversal of 21690663 is 36609612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21690663 - 2⁵ = 21690631 is a prime.

It is a super-2 number, since 2×21690663² = 940969722759138, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21690653) 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, 3615108 + ... + 3615113.

It is an arithmetic number, because the mean of its divisors is an integer number (7230222).

Almost surely, 2^21690663 is an apocalyptic number.

21690663 is a deficient number, since it is larger than the sum of its proper divisors (7230225).

21690663 is an equidigital number, since it uses as much as digits as its factorization.

21690663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7230224.

The product of its (nonzero) digits is 11664, while the sum is 33.

The square root of 21690663 is about 4657.3235876413. The cubic root of 21690663 is about 278.8844346086.

The spelling of 21690663 in words is "twenty-one million, six hundred ninety thousand, six hundred sixty-three".