21780432 has 30 divisors (see below), whose sum is σ = 60955362. Its totient is φ = 7260096.

The previous prime is 21780431. The next prime is 21780433. The reversal of 21780432 is 23408712.

It is an interprime number because it is at equal distance from previous prime (21780431) and next prime (21780433).

It can be written as a sum of positive squares in only one way, i.e., 21013056 + 767376 = 4584^2 + 876^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21780396 and 21780405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21780431) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 75483 + ... + 75770.

Almost surely, 2^21780432 is an apocalyptic number.

It is an amenable number.

21780432 is an abundant number, since it is smaller than the sum of its proper divisors (39174930).

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

21780432 is a wasteful number, since it uses less digits than its factorization.

21780432 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 151267 (or 151258 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21780432 is about 4666.9510389547. The cubic root of 21780432 is about 279.2686355454.

The spelling of 21780432 in words is "twenty-one million, seven hundred eighty thousand, four hundred thirty-two".