21369661 has 4 divisors (see below), whose sum is σ = 22494400. Its totient is φ = 20244924.

The previous prime is 21369659. The next prime is 21369679. The reversal of 21369661 is 16696312.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21369661 - 2¹ = 21369659 is a prime.

It is a super-2 number, since 2×21369661² = 913324822509842, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21364661) 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, 562341 + ... + 562378.

It is an arithmetic number, because the mean of its divisors is an integer number (5623600).

Almost surely, 2^21369661 is an apocalyptic number.

It is an amenable number.

21369661 is a deficient number, since it is larger than the sum of its proper divisors (1124739).

21369661 is a wasteful number, since it uses less digits than its factorization.

21369661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1124738.

The product of its digits is 11664, while the sum is 34.

The square root of 21369661 is about 4622.7330660552. The cubic root of 21369661 is about 277.5018466993.

The spelling of 21369661 in words is "twenty-one million, three hundred sixty-nine thousand, six hundred sixty-one".