21661036 has 6 divisors (see below), whose sum is σ = 37906820. Its totient is φ = 10830516.

The previous prime is 21661027. The next prime is 21661037. The reversal of 21661036 is 63016612.

It is a self number, because there is not a number n which added to its sum of digits gives 21661036.

It is not an unprimeable number, because it can be changed into a prime (21661037) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2707626 + ... + 2707633.

Almost surely, 2^21661036 is an apocalyptic number.

It is an amenable number.

21661036 is a deficient number, since it is larger than the sum of its proper divisors (16245784).

21661036 is a wasteful number, since it uses less digits than its factorization.

21661036 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5415263 (or 5415261 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 21661036 is about 4654.1418113332. The cubic root of 21661036 is about 278.7574018559.

Adding to 21661036 its reverse (63016612), we get a palindrome (84677648).

The spelling of 21661036 in words is "twenty-one million, six hundred sixty-one thousand, thirty-six".