21428745 has 16 divisors (see below), whose sum is σ = 36923712. Its totient is φ = 10549440.

The previous prime is 21428731. The next prime is 21428747. The reversal of 21428745 is 54782412.

It is not a de Polignac number, because 21428745 - 2⁶ = 21428681 is a prime.

It is a super-2 number, since 2×21428745² = 918382224550050, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21428747) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54751 + ... + 55140.

It is an arithmetic number, because the mean of its divisors is an integer number (2307732).

Almost surely, 2^21428745 is an apocalyptic number.

It is an amenable number.

21428745 is a deficient number, since it is larger than the sum of its proper divisors (15494967).

21428745 is a wasteful number, since it uses less digits than its factorization.

21428745 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109912.

The product of its digits is 17920, while the sum is 33.

The square root of 21428745 is about 4629.1192466818. The cubic root of 21428745 is about 277.7573620847.

The spelling of 21428745 in words is "twenty-one million, four hundred twenty-eight thousand, seven hundred forty-five".