21817642 has 48 divisors (see below), whose sum is σ = 42730848. Its totient is φ = 8255520.

The previous prime is 21817619. The next prime is 21817693. The reversal of 21817642 is 24671812.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39613 + ... + 40159.

It is an arithmetic number, because the mean of its divisors is an integer number (890226).

Almost surely, 2^21817642 is an apocalyptic number.

21817642 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21817642 is a deficient number, since it is larger than the sum of its proper divisors (20913206).

21817642 is a wasteful number, since it uses less digits than its factorization.

21817642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 611 (or 604 counting only the distinct ones).

The product of its digits is 5376, while the sum is 31.

The square root of 21817642 is about 4670.9358805276. The cubic root of 21817642 is about 279.4275805689.

The spelling of 21817642 in words is "twenty-one million, eight hundred seventeen thousand, six hundred forty-two".