21781052 has 6 divisors (see below), whose sum is σ = 38116848. Its totient is φ = 10890524.

The previous prime is 21781021. The next prime is 21781093. The reversal of 21781052 is 25018712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2722628 + ... + 2722635.

It is an arithmetic number, because the mean of its divisors is an integer number (6352808).

Almost surely, 2^21781052 is an apocalyptic number.

It is an amenable number.

21781052 is a deficient number, since it is larger than the sum of its proper divisors (16335796).

21781052 is a wasteful number, since it uses less digits than its factorization.

21781052 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5445267 (or 5445265 counting only the distinct ones).

The product of its (nonzero) digits is 1120, while the sum is 26.

The square root of 21781052 is about 4667.0174630057. The cubic root of 21781052 is about 279.2712853996.

Adding to 21781052 its reverse (25018712), we get a palindrome (46799764).

The spelling of 21781052 in words is "twenty-one million, seven hundred eighty-one thousand, fifty-two".