21519851 has 2 divisors, whose sum is σ = 21519852. Its totient is φ = 21519850.

The previous prime is 21519847. The next prime is 21519857. The reversal of 21519851 is 15891512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21519851 - 2² = 21519847 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21519857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10759925 + 10759926.

It is an arithmetic number, because the mean of its divisors is an integer number (10759926).

Almost surely, 2^21519851 is an apocalyptic number.

21519851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21519851 is an equidigital number, since it uses as much as digits as its factorization.

21519851 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3600, while the sum is 32.

The square root of 21519851 is about 4638.9493422541. The cubic root of 21519851 is about 278.1504413204.

The spelling of 21519851 in words is "twenty-one million, five hundred nineteen thousand, eight hundred fifty-one".