21651144 has 32 divisors (see below), whose sum is σ = 55875840. Its totient is φ = 6984000.

The previous prime is 21651121. The next prime is 21651163. The reversal of 21651144 is 44115612.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 13807 + ... + 15294.

It is an arithmetic number, because the mean of its divisors is an integer number (1746120).

Almost surely, 2^21651144 is an apocalyptic number.

21651144 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21651144 is an abundant number, since it is smaller than the sum of its proper divisors (34224696).

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

21651144 is a wasteful number, since it uses less digits than its factorization.

21651144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29141 (or 29137 counting only the distinct ones).

The product of its digits is 960, while the sum is 24.

The square root of 21651144 is about 4653.0789806321. The cubic root of 21651144 is about 278.7149617793.

Adding to 21651144 its reverse (44115612), we get a palindrome (65766756).

It can be divided in two parts, 216 and 51144, that added together give a triangular number (51360 = T₃₂₀).

The spelling of 21651144 in words is "twenty-one million, six hundred fifty-one thousand, one hundred forty-four".