21661744 has 30 divisors (see below), whose sum is σ = 45452076. Its totient is φ = 9996480.

The previous prime is 21661733. The next prime is 21661781. The reversal of 21661744 is 44716612.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1302 + ... + 6709.

Almost surely, 2^21661744 is an apocalyptic number.

It is an amenable number.

21661744 is an abundant number, since it is smaller than the sum of its proper divisors (23790332).

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

21661744 is a wasteful number, since it uses less digits than its factorization.

21661744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8045 (or 8026 counting only the distinct ones).

The product of its digits is 8064, while the sum is 31.

The square root of 21661744 is about 4654.2178719953. The cubic root of 21661744 is about 278.7604389235.

The spelling of 21661744 in words is "twenty-one million, six hundred sixty-one thousand, seven hundred forty-four".