21275784 has 40 divisors (see below), whose sum is σ = 59593710. Its totient is φ = 7091712.

The previous prime is 21275747. The next prime is 21275809. The reversal of 21275784 is 48757212.

It can be written as a sum of positive squares in only one way, i.e., 16990884 + 4284900 = 4122^2 + 2070^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 15769 + ... + 17064.

Almost surely, 2^21275784 is an apocalyptic number.

21275784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21275784 is an abundant number, since it is smaller than the sum of its proper divisors (38317926).

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

21275784 is a wasteful number, since it uses less digits than its factorization.

21275784 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32851 (or 32838 counting only the distinct ones).

The product of its digits is 31360, while the sum is 36.

The square root of 21275784 is about 4612.5680482785. The cubic root of 21275784 is about 277.0948946552.

The spelling of 21275784 in words is "twenty-one million, two hundred seventy-five thousand, seven hundred eighty-four".