21801649 has 8 divisors (see below), whose sum is σ = 23281920. Its totient is φ = 20370000.

The previous prime is 21801641. The next prime is 21801653. The reversal of 21801649 is 94610812.

It is a happy number.

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 21801649 - 2³ = 21801641 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21801649.

It is not an unprimeable number, because it can be changed into a prime (21801641) 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, 11227 + ... + 13024.

It is an arithmetic number, because the mean of its divisors is an integer number (2910240).

Almost surely, 2^21801649 is an apocalyptic number.

21801649 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21801649 is a deficient number, since it is larger than the sum of its proper divisors (1480271).

21801649 is a wasteful number, since it uses less digits than its factorization.

21801649 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24311.

The product of its (nonzero) digits is 3456, while the sum is 31.

The square root of 21801649 is about 4669.2235971305. The cubic root of 21801649 is about 279.3592875535.

The spelling of 21801649 in words is "twenty-one million, eight hundred one thousand, six hundred forty-nine".