21656061 has 24 divisors (see below), whose sum is σ = 36021440. Its totient is φ = 12280896.

The previous prime is 21656057. The next prime is 21656081. The reversal of 21656061 is 16065612.

It is a happy number.

21656061 is a `hidden beast` number, since 2 + 1 + 656 + 0 + 6 + 1 = 666.

It is not a de Polignac number, because 21656061 - 2² = 21656057 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656021) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7521 + ... + 9993.

Almost surely, 2^21656061 is an apocalyptic number.

21656061 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21656061 is a deficient number, since it is larger than the sum of its proper divisors (14365379).

21656061 is a wasteful number, since it uses less digits than its factorization.

21656061 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2625 (or 2622 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 21656061 is about 4653.6073104636. The cubic root of 21656061 is about 278.7360590131.

The spelling of 21656061 in words is "twenty-one million, six hundred fifty-six thousand, sixty-one".