21780223 has 8 divisors (see below), whose sum is σ = 22387968. Its totient is φ = 21178584.

The previous prime is 21780217. The next prime is 21780229. The reversal of 21780223 is 32208712.

It is an interprime number because it is at equal distance from previous prime (21780217) and next prime (21780229).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21780223 - 2²¹ = 19683071 is a prime.

It is a super-2 number, since 2×21780223² = 948756227859458, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21780229) 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, 6240 + ... + 9082.

It is an arithmetic number, because the mean of its divisors is an integer number (2798496).

Almost surely, 2^21780223 is an apocalyptic number.

21780223 is a deficient number, since it is larger than the sum of its proper divisors (607745).

21780223 is a wasteful number, since it uses less digits than its factorization.

21780223 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3053.

The product of its (nonzero) digits is 1344, while the sum is 25.

The square root of 21780223 is about 4666.9286474083. The cubic root of 21780223 is about 279.2677422767.

Adding to 21780223 its reverse (32208712), we get a palindrome (53988935).

It can be divided in two parts, 2 and 1780223, that multiplied together give a triangular number (3560446 = T₂₆₆₈).

The spelling of 21780223 in words is "twenty-one million, seven hundred eighty thousand, two hundred twenty-three".