21551797 has 8 divisors (see below), whose sum is σ = 22211000. Its totient is φ = 20896704.

The previous prime is 21551791. The next prime is 21551819. The reversal of 21551797 is 79715512.

It can be written as a sum of positive squares in 4 ways, for example, as 10201636 + 11350161 = 3194^2 + 3369^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21551797 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (37).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 12079 + ... + 13747.

It is an arithmetic number, because the mean of its divisors is an integer number (2776375).

Almost surely, 2^21551797 is an apocalyptic number.

It is an amenable number.

21551797 is a deficient number, since it is larger than the sum of its proper divisors (659203).

21551797 is a wasteful number, since it uses less digits than its factorization.

21551797 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2055.

The product of its digits is 22050, while the sum is 37.

The square root of 21551797 is about 4642.3913019047. The cubic root of 21551797 is about 278.2880104368.

The spelling of 21551797 in words is "twenty-one million, five hundred fifty-one thousand, seven hundred ninety-seven".