21123345 has 32 divisors (see below), whose sum is σ = 35902080.
Its totient is φ = 10575360.
The previous prime is 21123331. The next prime is 21123359. The reversal of 21123345 is 54332112.
It is an interprime number because it is at equal distance from previous prime (21123331) and next prime (21123359).
It is not a de Polignac number, because 21123345 - 25 = 21123313 is a prime.
It is an unprimeable number.
It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 38775 + ... + 39315.
It is an arithmetic number, because the mean of its divisors is an integer number (1121940).
Almost surely, 221123345 is an apocalyptic number.
It is an amenable number.
21123345 is a deficient number, since it is larger than the sum of its proper divisors (14778735).
21123345 is a wasteful number, since it uses less digits than its factorization.
21123345 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 705.
The product of its digits is 720, while the sum is 21.
The square root of 21123345 is about 4596.0140339211.
The cubic root of 21123345 is about 276.4315214640.
Adding to 21123345 its reverse (54332112), we get a palindrome (75455457).
The spelling of 21123345 in words is "twenty-one million, one hundred twenty-three thousand, three hundred forty-five".