21021401 has 4 divisors (see below), whose sum is σ = 22257972. Its totient is φ = 19784832.

The previous prime is 21021389. The next prime is 21021419. The reversal of 21021401 is 10412012.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 19758025 + 1263376 = 4445^2 + 1124^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021401 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21021431) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 618260 + ... + 618293.

It is an arithmetic number, because the mean of its divisors is an integer number (5564493).

Almost surely, 2^21021401 is an apocalyptic number.

It is an amenable number.

21021401 is a deficient number, since it is larger than the sum of its proper divisors (1236571).

21021401 is a wasteful number, since it uses less digits than its factorization.

21021401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236570.

The product of its (nonzero) digits is 16, while the sum is 11.

The square root of 21021401 is about 4584.9101408861. The cubic root of 21021401 is about 275.9861060359.

Adding to 21021401 its reverse (10412012), we get a palindrome (31433413).

The spelling of 21021401 in words is "twenty-one million, twenty-one thousand, four hundred one".