21653956 has 6 divisors (see below), whose sum is σ = 37894430. Its totient is φ = 10826976.

The previous prime is 21653941. The next prime is 21653959. The reversal of 21653956 is 65935612.

It can be written as a sum of positive squares in only one way, i.e., 14976900 + 6677056 = 3870^2 + 2584^2 .

It is not an unprimeable number, because it can be changed into a prime (21653959) 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, 2706741 + ... + 2706748.

Almost surely, 2^21653956 is an apocalyptic number.

It is an amenable number.

21653956 is a deficient number, since it is larger than the sum of its proper divisors (16240474).

21653956 is a wasteful number, since it uses less digits than its factorization.

21653956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5413493 (or 5413491 counting only the distinct ones).

The product of its digits is 48600, while the sum is 37.

The square root of 21653956 is about 4653.3811363352. The cubic root of 21653956 is about 278.7270275397.

The spelling of 21653956 in words is "twenty-one million, six hundred fifty-three thousand, nine hundred fifty-six".