21311956 has 6 divisors (see below), whose sum is σ = 37295930. Its totient is φ = 10655976.

The previous prime is 21311951. The next prime is 21311957. The reversal of 21311956 is 65911312.

It can be written as a sum of positive squares in only one way, i.e., 19061956 + 2250000 = 4366^2 + 1500^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21311951) 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, 2663991 + ... + 2663998.

Almost surely, 2^21311956 is an apocalyptic number.

It is an amenable number.

21311956 is a deficient number, since it is larger than the sum of its proper divisors (15983974).

21311956 is a wasteful number, since it uses less digits than its factorization.

21311956 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5327993 (or 5327991 counting only the distinct ones).

The product of its digits is 1620, while the sum is 28.

The square root of 21311956 is about 4616.4874092756. The cubic root of 21311956 is about 277.2518399354.

The spelling of 21311956 in words is "twenty-one million, three hundred eleven thousand, nine hundred fifty-six".