21661072 has 20 divisors (see below), whose sum is σ = 42040960. Its totient is φ = 10811808.

The previous prime is 21661061. The next prime is 21661097. The reversal of 21661072 is 27016612.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15973 + ... + 17275.

It is an arithmetic number, because the mean of its divisors is an integer number (2102048).

Almost surely, 2^21661072 is an apocalyptic number.

It is an amenable number.

21661072 is a deficient number, since it is larger than the sum of its proper divisors (20379888).

21661072 is a wasteful number, since it uses less digits than its factorization.

21661072 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2350 (or 2344 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21661072 is about 4654.1456788545. The cubic root of 21661072 is about 278.7575562847.

Adding to 21661072 its reverse (27016612), we get a palindrome (48677684).

The spelling of 21661072 in words is "twenty-one million, six hundred sixty-one thousand, seventy-two".