21477561 has 32 divisors (see below), whose sum is σ = 34836480. Its totient is φ = 11504064.

The previous prime is 21477559. The next prime is 21477583. The reversal of 21477561 is 16577412.

It is not a de Polignac number, because 21477561 - 2¹ = 21477559 is a prime.

It is a super-2 number, since 2×21477561² = 922571253017442, which contains 22 as substring.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21477541) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 25180 + ... + 26018.

It is an arithmetic number, because the mean of its divisors is an integer number (1088640).

Almost surely, 2^21477561 is an apocalyptic number.

21477561 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21477561 is a deficient number, since it is larger than the sum of its proper divisors (13358919).

21477561 is a wasteful number, since it uses less digits than its factorization.

21477561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 925.

The product of its digits is 11760, while the sum is 33.

The square root of 21477561 is about 4634.3889564861. The cubic root of 21477561 is about 277.9681182492.

The spelling of 21477561 in words is "twenty-one million, four hundred seventy-seven thousand, five hundred sixty-one".