21512401 has 2 divisors, whose sum is σ = 21512402. Its totient is φ = 21512400.

The previous prime is 21512371. The next prime is 21512431. The reversal of 21512401 is 10421512.

It is a balanced prime because it is at equal distance from previous prime (21512371) and next prime (21512431).

It can be written as a sum of positive squares in only one way, i.e., 13395600 + 8116801 = 3660^2 + 2849^2 .

It is a cyclic number.

It is not a de Polignac number, because 21512401 - 2⁷ = 21512273 is a prime.

It is a super-3 number, since 3×21512401³ (a number of 23 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (21512431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10756200 + 10756201.

It is an arithmetic number, because the mean of its divisors is an integer number (10756201).

Almost surely, 2^21512401 is an apocalyptic number.

It is an amenable number.

21512401 is a deficient number, since it is larger than the sum of its proper divisors (1).

21512401 is an equidigital number, since it uses as much as digits as its factorization.

21512401 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 80, while the sum is 16.

The square root of 21512401 is about 4638.1462891979. The cubic root of 21512401 is about 278.1183397976.

Adding to 21512401 its reverse (10421512), we get a palindrome (31933913).

The spelling of 21512401 in words is "twenty-one million, five hundred twelve thousand, four hundred one".