21626661 has 8 divisors (see below), whose sum is σ = 32954944. Its totient is φ = 12358080.

The previous prime is 21626653. The next prime is 21626719. The reversal of 21626661 is 16662612.

21626661 is nontrivially palindromic in base 2.

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

It is not a de Polignac number, because 21626661 - 2³ = 21626653 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 (21626621) 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, 514900 + ... + 514941.

It is an arithmetic number, because the mean of its divisors is an integer number (4119368).

Almost surely, 2^21626661 is an apocalyptic number.

21626661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21626661 is a deficient number, since it is larger than the sum of its proper divisors (11328283).

21626661 is a wasteful number, since it uses less digits than its factorization.

21626661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1029851.

The product of its digits is 5184, while the sum is 30.

The square root of 21626661 is about 4650.4473978317. The cubic root of 21626661 is about 278.6098656834.

The spelling of 21626661 in words is "twenty-one million, six hundred twenty-six thousand, six hundred sixty-one".