21956686 has 4 divisors (see below), whose sum is σ = 32935032. Its totient is φ = 10978342.

The previous prime is 21956621. The next prime is 21956687. The reversal of 21956686 is 68665912.

It is a semiprime because it is the product of two primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21956687) 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, 5489170 + ... + 5489173.

It is an arithmetic number, because the mean of its divisors is an integer number (8233758).

Almost surely, 2^21956686 is an apocalyptic number.

21956686 is a deficient number, since it is larger than the sum of its proper divisors (10978346).

21956686 is a wasteful number, since it uses less digits than its factorization.

21956686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10978345.

The product of its digits is 155520, while the sum is 43.

The square root of 21956686 is about 4685.7961970192. The cubic root of 21956686 is about 280.0199220519.

It can be divided in two parts, 21956 and 686, that multiplied together give a triangular number (15061816 = T₅₄₈₈).

The spelling of 21956686 in words is "twenty-one million, nine hundred fifty-six thousand, six hundred eighty-six".