21355481 has 4 divisors (see below), whose sum is σ = 24406272. Its totient is φ = 18304692.

The previous prime is 21355471. The next prime is 21355483. The reversal of 21355481 is 18455312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-21355481 is a prime.

It is a super-2 number, since 2×21355481² = 912113137482722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21355483) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1525385 + ... + 1525398.

It is an arithmetic number, because the mean of its divisors is an integer number (6101568).

Almost surely, 2^21355481 is an apocalyptic number.

It is an amenable number.

21355481 is a deficient number, since it is larger than the sum of its proper divisors (3050791).

21355481 is an equidigital number, since it uses as much as digits as its factorization.

21355481 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3050790.

The product of its digits is 4800, while the sum is 29.

The square root of 21355481 is about 4621.1990868172. The cubic root of 21355481 is about 277.4404536357.

The spelling of 21355481 in words is "twenty-one million, three hundred fifty-five thousand, four hundred eighty-one".