21956397 has 8 divisors (see below), whose sum is σ = 29298720. Its totient is φ = 14625840.

The previous prime is 21956351. The next prime is 21956399. The reversal of 21956397 is 79365912.

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

It is not a de Polignac number, because 21956397 - 2⁷ = 21956269 is a prime.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21956399) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3322 + ... + 7412.

It is an arithmetic number, because the mean of its divisors is an integer number (3662340).

Almost surely, 2^21956397 is an apocalyptic number.

It is an amenable number.

21956397 is a deficient number, since it is larger than the sum of its proper divisors (7342323).

21956397 is a wasteful number, since it uses less digits than its factorization.

21956397 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5883.

The product of its digits is 102060, while the sum is 42.

The square root of 21956397 is about 4685.7653590422. The cubic root of 21956397 is about 280.0186934798.

It can be divided in two parts, 219 and 56397, that added together give a triangular number (56616 = T₃₃₆).

The spelling of 21956397 in words is "twenty-one million, nine hundred fifty-six thousand, three hundred ninety-seven".