21919501 has 2 divisors, whose sum is σ = 21919502. Its totient is φ = 21919500.

The previous prime is 21919487. The next prime is 21919507. The reversal of 21919501 is 10591912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13682601 + 8236900 = 3699^2 + 2870^2 .

It is a cyclic number.

It is not a de Polignac number, because 21919501 - 2²³ = 13530893 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21919501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21919507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10959750 + 10959751.

It is an arithmetic number, because the mean of its divisors is an integer number (10959751).

Almost surely, 2^21919501 is an apocalyptic number.

It is an amenable number.

21919501 is a deficient number, since it is larger than the sum of its proper divisors (1).

21919501 is an equidigital number, since it uses as much as digits as its factorization.

21919501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 810, while the sum is 28.

The square root of 21919501 is about 4681.8266734257. The cubic root of 21919501 is about 279.8617557356.

The spelling of 21919501 in words is "twenty-one million, nine hundred nineteen thousand, five hundred one".