21781492 has 12 divisors (see below), whose sum is σ = 38928960. Its totient is φ = 10658936.

The previous prime is 21781481. The next prime is 21781511. The reversal of 21781492 is 29418712.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 57742 + ... + 58117.

It is an arithmetic number, because the mean of its divisors is an integer number (3244080).

Almost surely, 2^21781492 is an apocalyptic number.

It is an amenable number.

21781492 is a deficient number, since it is larger than the sum of its proper divisors (17147468).

21781492 is a wasteful number, since it uses less digits than its factorization.

21781492 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115910 (or 115908 counting only the distinct ones).

The product of its digits is 8064, while the sum is 34.

The square root of 21781492 is about 4667.0646020813. The cubic root of 21781492 is about 279.2731659108.

The spelling of 21781492 in words is "twenty-one million, seven hundred eighty-one thousand, four hundred ninety-two".