21745789 has 4 divisors (see below), whose sum is σ = 23418556. Its totient is φ = 20073024.

The previous prime is 21745783. The next prime is 21745799. The reversal of 21745789 is 98754712.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12996025 + 8749764 = 3605^2 + 2958^2 .

It is a cyclic number.

It is not a de Polignac number, because 21745789 - 2³ = 21745781 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21745781) 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, 836364 + ... + 836389.

It is an arithmetic number, because the mean of its divisors is an integer number (5854639).

Almost surely, 2^21745789 is an apocalyptic number.

It is an amenable number.

21745789 is a deficient number, since it is larger than the sum of its proper divisors (1672767).

21745789 is a wasteful number, since it uses less digits than its factorization.

21745789 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1672766.

The product of its digits is 141120, while the sum is 43.

The square root of 21745789 is about 4663.2380381019. The cubic root of 21745789 is about 279.1204928262.

The spelling of 21745789 in words is "twenty-one million, seven hundred forty-five thousand, seven hundred eighty-nine".