21621307 has 4 divisors (see below), whose sum is σ = 21812760. Its totient is φ = 21429856.

The previous prime is 21621293. The next prime is 21621329. The reversal of 21621307 is 70312612.

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

It is a cyclic number.

It is not a de Polignac number, because 21621307 - 2⁷ = 21621179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21621337) 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, 95557 + ... + 95782.

It is an arithmetic number, because the mean of its divisors is an integer number (5453190).

Almost surely, 2^21621307 is an apocalyptic number.

21621307 is a deficient number, since it is larger than the sum of its proper divisors (191453).

21621307 is a wasteful number, since it uses less digits than its factorization.

21621307 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191452.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 21621307 is about 4649.8717186606. The cubic root of 21621307 is about 278.5868724539.

Adding to 21621307 its reverse (70312612), we get a palindrome (91933919).

The spelling of 21621307 in words is "twenty-one million, six hundred twenty-one thousand, three hundred seven".