21561798 has 8 divisors (see below), whose sum is σ = 43123608. Its totient is φ = 7187264.

The previous prime is 21561781. The next prime is 21561817. The reversal of 21561798 is 89716512.

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

21561798 is an admirable number.

It is a super-2 number, since 2×21561798² = 929822265985608, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1796811 + ... + 1796822.

It is an arithmetic number, because the mean of its divisors is an integer number (5390451).

Almost surely, 2^21561798 is an apocalyptic number.

21561798 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21561798 is a wasteful number, since it uses less digits than its factorization.

21561798 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3593638.

The product of its digits is 30240, while the sum is 39.

The square root of 21561798 is about 4643.4683158174. The cubic root of 21561798 is about 278.3310498177.

The spelling of 21561798 in words is "twenty-one million, five hundred sixty-one thousand, seven hundred ninety-eight".