21661704 has 24 divisors (see below), whose sum is σ = 58667310. Its totient is φ = 7220544.

The previous prime is 21661693. The next prime is 21661709. The reversal of 21661704 is 40716612.

It can be written as a sum of positive squares in only one way, i.e., 21622500 + 39204 = 4650^2 + 198^2 .

It is a tau number, because it is divible by the number of its divisors (24).

It is not an unprimeable number, because it can be changed into a prime (21661709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 150357 + ... + 150500.

Almost surely, 2^21661704 is an apocalyptic number.

21661704 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21661704 is an abundant number, since it is smaller than the sum of its proper divisors (37005606).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21661704 is a wasteful number, since it uses less digits than its factorization.

21661704 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 300869 (or 300862 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21661704 is about 4654.2135748158. The cubic root of 21661704 is about 278.7602673395.

The spelling of 21661704 in words is "twenty-one million, six hundred sixty-one thousand, seven hundred four".