21779772 has 48 divisors (see below), whose sum is σ = 58367232. Its totient is φ = 6192000.

The previous prime is 21779761. The next prime is 21779773. The reversal of 21779772 is 27797712.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21779773) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20568 + ... + 21600.

It is an arithmetic number, because the mean of its divisors is an integer number (1215984).

Almost surely, 2^21779772 is an apocalyptic number.

It is an amenable number.

21779772 is an abundant number, since it is smaller than the sum of its proper divisors (36587460).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21779772 is a wasteful number, since it uses less digits than its factorization.

21779772 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1298 (or 1296 counting only the distinct ones).

The product of its digits is 86436, while the sum is 42.

The square root of 21779772 is about 4666.8803284421. The cubic root of 21779772 is about 279.2658146775.

The spelling of 21779772 in words is "twenty-one million, seven hundred seventy-nine thousand, seven hundred seventy-two".