21745161 has 12 divisors (see below), whose sum is σ = 32078592. Its totient is φ = 14188056.

The previous prime is 21745151. The next prime is 21745181. The reversal of 21745161 is 16154712.

It is a happy number.

It is not a de Polignac number, because 21745161 - 2⁷ = 21745033 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21745121) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 25281 + ... + 26126.

It is an arithmetic number, because the mean of its divisors is an integer number (2673216).

Almost surely, 2^21745161 is an apocalyptic number.

It is an amenable number.

21745161 is a deficient number, since it is larger than the sum of its proper divisors (10333431).

21745161 is a wasteful number, since it uses less digits than its factorization.

21745161 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 51460 (or 51457 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 21745161 is about 4663.1707024298. The cubic root of 21745161 is about 279.1178058790.

Adding to 21745161 its reverse (16154712), we get a palindrome (37899873).

The spelling of 21745161 in words is "twenty-one million, seven hundred forty-five thousand, one hundred sixty-one".