21756642 has 16 divisors (see below), whose sum is σ = 44163552. Its totient is φ = 7143840.

The previous prime is 21756613. The next prime is 21756649. The reversal of 21756642 is 24665712.

It is a super-2 number, since 2×21756642² = 946702942232328, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21756649) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 26659 + ... + 27462.

It is an arithmetic number, because the mean of its divisors is an integer number (2760222).

Almost surely, 2^21756642 is an apocalyptic number.

21756642 is an abundant number, since it is smaller than the sum of its proper divisors (22406910).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21756642 is a wasteful number, since it uses less digits than its factorization.

21756642 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54193.

The product of its digits is 20160, while the sum is 33.

The square root of 21756642 is about 4664.4015693334. The cubic root of 21756642 is about 279.1669200661.

The spelling of 21756642 in words is "twenty-one million, seven hundred fifty-six thousand, six hundred forty-two".