21065761 has 4 divisors (see below), whose sum is σ = 21124800. Its totient is φ = 21006724.

The previous prime is 21065753. The next prime is 21065767. The reversal of 21065761 is 16756012.

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 cyclic number.

It is not a de Polignac number, because 21065761 - 2³ = 21065753 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21065767) 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, 28981 + ... + 29698.

It is an arithmetic number, because the mean of its divisors is an integer number (5281200).

Almost surely, 2^21065761 is an apocalyptic number.

It is an amenable number.

21065761 is a deficient number, since it is larger than the sum of its proper divisors (59039).

21065761 is an equidigital number, since it uses as much as digits as its factorization.

21065761 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 59038.

The product of its (nonzero) digits is 2520, while the sum is 28.

The square root of 21065761 is about 4589.7451998994. The cubic root of 21065761 is about 276.1801010678.

The spelling of 21065761 in words is "twenty-one million, sixty-five thousand, seven hundred sixty-one".