21090742 has 8 divisors (see below), whose sum is σ = 31656456. Its totient is φ = 10538592.

The previous prime is 21090731. The next prime is 21090791. The reversal of 21090742 is 24709012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×21090742² = 889638796221128, which contains 22 as substring.

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, 2653 + ... + 7015.

It is an arithmetic number, because the mean of its divisors is an integer number (3957057).

Almost surely, 2^21090742 is an apocalyptic number.

21090742 is a deficient number, since it is larger than the sum of its proper divisors (10565714).

21090742 is a wasteful number, since it uses less digits than its factorization.

21090742 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6782.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21090742 is about 4592.4657864812. The cubic root of 21090742 is about 276.2892280649.

Adding to 21090742 its reverse (24709012), we get a palindrome (45799754).

The spelling of 21090742 in words is "twenty-one million, ninety thousand, seven hundred forty-two".