21101660 has 12 divisors (see below), whose sum is σ = 44313528. Its totient is φ = 8440656.

The previous prime is 21101651. The next prime is 21101677. The reversal of 21101660 is 6610112.

It is a happy number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 527522 + ... + 527561.

It is an arithmetic number, because the mean of its divisors is an integer number (3692794).

Almost surely, 2^21101660 is an apocalyptic number.

21101660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21101660 is an abundant number, since it is smaller than the sum of its proper divisors (23211868).

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

21101660 is a wasteful number, since it uses less digits than its factorization.

21101660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1055092 (or 1055090 counting only the distinct ones).

The product of its (nonzero) digits is 72, while the sum is 17.

The square root of 21101660 is about 4593.6543187314. The cubic root of 21101660 is about 276.3368951949.

Adding to 21101660 its reverse (6610112), we get a palindrome (27711772).

The spelling of 21101660 in words is "twenty-one million, one hundred one thousand, six hundred sixty".