21656090 has 16 divisors (see below), whose sum is σ = 39888288. Its totient is φ = 8460816.

The previous prime is 21656081. The next prime is 21656093. The reversal of 21656090 is 9065612.

It is not an unprimeable number, because it can be changed into a prime (21656093) 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 in 7 ways as a sum of consecutive naturals, for example, 24752 + ... + 25611.

It is an arithmetic number, because the mean of its divisors is an integer number (2493018).

Almost surely, 2^21656090 is an apocalyptic number.

21656090 is a deficient number, since it is larger than the sum of its proper divisors (18232198).

21656090 is a wasteful number, since it uses less digits than its factorization.

21656090 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50413.

The product of its (nonzero) digits is 3240, while the sum is 29.

The square root of 21656090 is about 4653.6104263249. The cubic root of 21656090 is about 278.7361834331.

The spelling of 21656090 in words is "twenty-one million, six hundred fifty-six thousand, ninety".