21551061 has 16 divisors (see below), whose sum is σ = 32911488. Its totient is φ = 12288000.

The previous prime is 21551039. The next prime is 21551071. The reversal of 21551061 is 16015512.

It is not a de Polignac number, because 21551061 - 2²¹ = 19453909 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551071) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12661 + ... + 14261.

It is an arithmetic number, because the mean of its divisors is an integer number (2056968).

Almost surely, 2^21551061 is an apocalyptic number.

21551061 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21551061 is a deficient number, since it is larger than the sum of its proper divisors (11360427).

21551061 is a wasteful number, since it uses less digits than its factorization.

21551061 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2252.

The product of its (nonzero) digits is 300, while the sum is 21.

The square root of 21551061 is about 4642.3120317359. The cubic root of 21551061 is about 278.2848425292.

Adding to 21551061 its reverse (16015512), we get a palindrome (37566573).

The spelling of 21551061 in words is "twenty-one million, five hundred fifty-one thousand, sixty-one".