21542993 has 2 divisors, whose sum is σ = 21542994. Its totient is φ = 21542992.

The previous prime is 21542977. The next prime is 21543001. The reversal of 21542993 is 39924512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21418384 + 124609 = 4628^2 + 353^2 .

It is a cyclic number.

It is not a de Polignac number, because 21542993 - 2⁴ = 21542977 is a prime.

It is not a weakly prime, because it can be changed into another prime (21542953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771496 + 10771497.

It is an arithmetic number, because the mean of its divisors is an integer number (10771497).

Almost surely, 2^21542993 is an apocalyptic number.

It is an amenable number.

21542993 is a deficient number, since it is larger than the sum of its proper divisors (1).

21542993 is an equidigital number, since it uses as much as digits as its factorization.

21542993 is an evil number, because the sum of its binary digits is even.

The product of its digits is 19440, while the sum is 35.

The square root of 21542993 is about 4641.4429868307. The cubic root of 21542993 is about 278.2501113336.

The spelling of 21542993 in words is "twenty-one million, five hundred forty-two thousand, nine hundred ninety-three".