21256361 has 8 divisors (see below), whose sum is σ = 24810240. Its totient is φ = 17831808.

The previous prime is 21256331. The next prime is 21256369. The reversal of 21256361 is 16365212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21256361 - 2¹⁸ = 20994217 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a self number, because there is not a number n which added to its sum of digits gives 21256361.

It is not an unprimeable number, because it can be changed into a prime (21256369) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31976 + ... + 32633.

It is an arithmetic number, because the mean of its divisors is an integer number (3101280).

Almost surely, 2^21256361 is an apocalyptic number.

It is an amenable number.

21256361 is a deficient number, since it is larger than the sum of its proper divisors (3553879).

21256361 is an equidigital number, since it uses as much as digits as its factorization.

21256361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64663.

The product of its digits is 2160, while the sum is 26.

The square root of 21256361 is about 4610.4621243429. The cubic root of 21256361 is about 277.0105475442.

The spelling of 21256361 in words is "twenty-one million, two hundred fifty-six thousand, three hundred sixty-one".