21564740 has 24 divisors (see below), whose sum is σ = 45444672. Its totient is φ = 8595680.

The previous prime is 21564733. The next prime is 21564743. The reversal of 21564740 is 4746512.

21564740 = 363² + 364² + ... + 482².

It is a super-2 number, since 2×21564740² = 930076022535200, which contains 22 as substring.

It is a plaindrome in base 11.

It is a zygodrome in base 11.

It is not an unprimeable number, because it can be changed into a prime (21564743) 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, 4487 + ... + 7953.

It is an arithmetic number, because the mean of its divisors is an integer number (1893528).

Almost surely, 2^21564740 is an apocalyptic number.

21564740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21564740 is an abundant number, since it is smaller than the sum of its proper divisors (23879932).

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

21564740 is a wasteful number, since it uses less digits than its factorization.

21564740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3787 (or 3785 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 29.

The square root of 21564740 is about 4643.7850940800. The cubic root of 21564740 is about 278.3437082041.

The spelling of 21564740 in words is "twenty-one million, five hundred sixty-four thousand, seven hundred forty".