21550537 has 2 divisors, whose sum is σ = 21550538. Its totient is φ = 21550536.

The previous prime is 21550519. The next prime is 21550547. The reversal of 21550537 is 73505512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10916416 + 10634121 = 3304^2 + 3261^2 .

It is a cyclic number.

It is not a de Polignac number, because 21550537 - 2⁷ = 21550409 is a prime.

It is equal to p_1362574 and since 21550537 and 1362574 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21550547) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775268 + 10775269.

It is an arithmetic number, because the mean of its divisors is an integer number (10775269).

Almost surely, 2^21550537 is an apocalyptic number.

It is an amenable number.

21550537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21550537 is an equidigital number, since it uses as much as digits as its factorization.

21550537 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5250, while the sum is 28.

The square root of 21550537 is about 4642.2555939974. The cubic root of 21550537 is about 278.2825870727.

The spelling of 21550537 in words is "twenty-one million, five hundred fifty thousand, five hundred thirty-seven".