21401621 has 8 divisors (see below), whose sum is σ = 21645624. Its totient is φ = 21159360.

The previous prime is 21401617. The next prime is 21401641. The reversal of 21401621 is 12610412.

It can be written as a sum of positive squares in 4 ways, for example, as 835396 + 20566225 = 914^2 + 4535^2 .

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 21401621 - 2² = 21401617 is a prime.

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 21401621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21401641) 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, 57191 + ... + 57563.

It is an arithmetic number, because the mean of its divisors is an integer number (2705703).

Almost surely, 2^21401621 is an apocalyptic number.

It is an amenable number.

21401621 is a deficient number, since it is larger than the sum of its proper divisors (244003).

21401621 is a wasteful number, since it uses less digits than its factorization.

21401621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 871.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 21401621 is about 4626.1886040238. The cubic root of 21401621 is about 277.6401196974.

It can be divided in two parts, 21401 and 621, that added together give a palindrome (22022).

The spelling of 21401621 in words is "twenty-one million, four hundred one thousand, six hundred twenty-one".