21751660 has 48 divisors (see below), whose sum is σ = 52496640. Its totient is φ = 7416000.

The previous prime is 21751649. The next prime is 21751661. The reversal of 21751660 is 6615712.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is not an unprimeable number, because it can be changed into a prime (21751661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 34831 + ... + 35449.

It is an arithmetic number, because the mean of its divisors is an integer number (1093680).

Almost surely, 2^21751660 is an apocalyptic number.

21751660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21751660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26248320).

21751660 is an abundant number, since it is smaller than the sum of its proper divisors (30744980).

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

21751660 is a wasteful number, since it uses less digits than its factorization.

21751660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 886 (or 884 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21751660 is about 4663.8674938296. The cubic root of 21751660 is about 279.1456098570.

The spelling of 21751660 in words is "twenty-one million, seven hundred fifty-one thousand, six hundred sixty".