21690811 has 8 divisors (see below), whose sum is σ = 22604400. Its totient is φ = 20788320.

The previous prime is 21690803. The next prime is 21690821. The reversal of 21690811 is 11809612.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21690811 - 2³ = 21690803 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21690811.

It is not an unprimeable number, because it can be changed into a prime (21690821) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1341 + ... + 6721.

It is an arithmetic number, because the mean of its divisors is an integer number (2825550).

Almost surely, 2^21690811 is an apocalyptic number.

21690811 is a deficient number, since it is larger than the sum of its proper divisors (913589).

21690811 is a wasteful number, since it uses less digits than its factorization.

21690811 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5549.

The product of its (nonzero) digits is 864, while the sum is 28.

The square root of 21690811 is about 4657.3394765681. The cubic root of 21690811 is about 278.8850689031.

The spelling of 21690811 in words is "twenty-one million, six hundred ninety thousand, eight hundred eleven".