21772809 has 12 divisors (see below), whose sum is σ = 31829616. Its totient is φ = 14339832.

The previous prime is 21772787. The next prime is 21772811. The reversal of 21772809 is 90827712.

It is not a de Polignac number, because 21772809 - 2²⁰ = 20724233 is a prime.

It is a super-3 number, since 3×21772809³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (21772109) 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, 13827 + ... + 15320.

It is an arithmetic number, because the mean of its divisors is an integer number (2652468).

Almost surely, 2^21772809 is an apocalyptic number.

It is an amenable number.

21772809 is a deficient number, since it is larger than the sum of its proper divisors (10056807).

21772809 is a wasteful number, since it uses less digits than its factorization.

21772809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29236 (or 29233 counting only the distinct ones).

The product of its (nonzero) digits is 14112, while the sum is 36.

The square root of 21772809 is about 4666.1342672495. The cubic root of 21772809 is about 279.2360510490.

The spelling of 21772809 in words is "twenty-one million, seven hundred seventy-two thousand, eight hundred nine".