21172761 has 12 divisors (see below), whose sum is σ = 30768192. Its totient is φ = 14029656.

The previous prime is 21172757. The next prime is 21172763. The reversal of 21172761 is 16727112.

It is not a de Polignac number, because 21172761 - 2² = 21172757 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21172763) 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, 5541 + ... + 8546.

It is an arithmetic number, because the mean of its divisors is an integer number (2564016).

Almost surely, 2^21172761 is an apocalyptic number.

It is an amenable number.

21172761 is a deficient number, since it is larger than the sum of its proper divisors (9595431).

21172761 is a wasteful number, since it uses less digits than its factorization.

21172761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14260 (or 14257 counting only the distinct ones).

The product of its digits is 1176, while the sum is 27.

The square root of 21172761 is about 4601.3868561554. The cubic root of 21172761 is about 276.6469150913.

Adding to 21172761 its reverse (16727112), we get a palindrome (37899873).

The spelling of 21172761 in words is "twenty-one million, one hundred seventy-two thousand, seven hundred sixty-one".