21710661 has 8 divisors (see below), whose sum is σ = 33082944. Its totient is φ = 12406080.

The previous prime is 21710639. The next prime is 21710669. The reversal of 21710661 is 16601712.

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

It is not a de Polignac number, because 21710661 - 2⁹ = 21710149 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21710669) 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, 516900 + ... + 516941.

It is an arithmetic number, because the mean of its divisors is an integer number (4135368).

Almost surely, 2^21710661 is an apocalyptic number.

21710661 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21710661 is a deficient number, since it is larger than the sum of its proper divisors (11372283).

21710661 is a wasteful number, since it uses less digits than its factorization.

21710661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1033851.

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21710661 is about 4659.4700342421. The cubic root of 21710661 is about 278.9701153741.

It can be divided in two parts, 217 and 10661, that added together give a triangular number (10878 = T₁₄₇).

The spelling of 21710661 in words is "twenty-one million, seven hundred ten thousand, six hundred sixty-one".