21355965 has 24 divisors (see below), whose sum is σ = 37124568. Its totient is φ = 11356800.

The previous prime is 21355963. The next prime is 21355967. The reversal of 21355965 is 56955312.

It is an interprime number because it is at equal distance from previous prime (21355963) and next prime (21355967).

It can be written as a sum of positive squares in 4 ways, for example, as 12659364 + 8696601 = 3558^2 + 2949^2 .

It is not a de Polignac number, because 21355965 - 2¹ = 21355963 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21355963) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 30115 + ... + 30815.

It is an arithmetic number, because the mean of its divisors is an integer number (1546857).

Almost surely, 2^21355965 is an apocalyptic number.

It is an amenable number.

21355965 is a deficient number, since it is larger than the sum of its proper divisors (15768603).

21355965 is a wasteful number, since it uses less digits than its factorization.

21355965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1389 (or 1386 counting only the distinct ones).

The product of its digits is 40500, while the sum is 36.

The square root of 21355965 is about 4621.2514538813. The cubic root of 21355965 is about 277.4425495873.

It can be divided in two parts, 2135 and 5965, that added together give a square (8100 = 90²).

The spelling of 21355965 in words is "twenty-one million, three hundred fifty-five thousand, nine hundred sixty-five".