21621741 has 4 divisors (see below), whose sum is σ = 28828992. Its totient is φ = 14414492.

The previous prime is 21621737. The next prime is 21621757. The reversal of 21621741 is 14712612.

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 21621741 - 2² = 21621737 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621641) 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, 3603621 + ... + 3603626.

It is an arithmetic number, because the mean of its divisors is an integer number (7207248).

Almost surely, 2^21621741 is an apocalyptic number.

It is an amenable number.

21621741 is a deficient number, since it is larger than the sum of its proper divisors (7207251).

21621741 is an equidigital number, since it uses as much as digits as its factorization.

21621741 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7207250.

The product of its digits is 672, while the sum is 24.

The square root of 21621741 is about 4649.9183863806. The cubic root of 21621741 is about 278.5887364469.

The spelling of 21621741 in words is "twenty-one million, six hundred twenty-one thousand, seven hundred forty-one".