21620999 has 2 divisors, whose sum is σ = 21621000. Its totient is φ = 21620998.

The previous prime is 21620953. The next prime is 21621001. The reversal of 21620999 is 99902612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21620999 is a prime.

Together with 21621001, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21622999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10810499 + 10810500.

It is an arithmetic number, because the mean of its divisors is an integer number (10810500).

Almost surely, 2^21620999 is an apocalyptic number.

21620999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21620999 is an equidigital number, since it uses as much as digits as its factorization.

21620999 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 17496, while the sum is 38.

The square root of 21620999 is about 4649.8385993494. The cubic root of 21620999 is about 278.5855496051.

The spelling of 21620999 in words is "twenty-one million, six hundred twenty thousand, nine hundred ninety-nine".