21355642 has 32 divisors (see below), whose sum is σ = 40362624. Its totient is φ = 8232000.

The previous prime is 21355637. The next prime is 21355657. The reversal of 21355642 is 24655312.

It is a self number, because there is not a number n which added to its sum of digits gives 21355642.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14868 + ... + 16240.

It is an arithmetic number, because the mean of its divisors is an integer number (1261332).

Almost surely, 2^21355642 is an apocalyptic number.

21355642 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

21355642 is a deficient number, since it is larger than the sum of its proper divisors (19006982).

21355642 is a wasteful number, since it uses less digits than its factorization.

21355642 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1494.

The product of its digits is 7200, while the sum is 28.

The square root of 21355642 is about 4621.2165065056. The cubic root of 21355642 is about 277.4411508463.

It can be divided in two parts, 2135 and 5642, that added together give a palindrome (7777).

The spelling of 21355642 in words is "twenty-one million, three hundred fifty-five thousand, six hundred forty-two".