21694661 has 4 divisors (see below), whose sum is σ = 22199232. Its totient is φ = 21190092.

The previous prime is 21694657. The next prime is 21694663. The reversal of 21694661 is 16649612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21694661 - 2² = 21694657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21694663) 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, 252221 + ... + 252306.

It is an arithmetic number, because the mean of its divisors is an integer number (5549808).

Almost surely, 2^21694661 is an apocalyptic number.

It is an amenable number.

21694661 is a deficient number, since it is larger than the sum of its proper divisors (504571).

21694661 is an equidigital number, since it uses as much as digits as its factorization.

21694661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 504570.

The product of its digits is 15552, while the sum is 35.

The square root of 21694661 is about 4657.7527843371. The cubic root of 21694661 is about 278.9015681171.

The spelling of 21694661 in words is "twenty-one million, six hundred ninety-four thousand, six hundred sixty-one".